1 . With the weather getting colder and the days becoming shorter, some people are noticing they have less energy and aren’t feeling as positive as they usually do.    1    This type of depression is known as seasonal affective disorder (SAD).

Researchers aren’t yet clear on what causes SAD, but it's likely to be complex. Some research suggests it could be due to a malfunctioning hypothalamus (下丘脑功能不全) or producing too much melatonin (a hormone which controls our sleep-wake cycle). Some researchers theorize it could also be due to having a disrupted circadian rhythm(昼夜节奏混乱).    2    For example, some research has indicated that women may be more likely to experience SAD — though, due to a lack of specific research, it’s uncertain whether these gender differences really exist and if so, why.

Some people notice that their symptoms start to improve when the seasons begin to change and spring approaches.    3    For people with SAD, the main recommended treatments include psychological treatments or taking medicine. Research shows that cognitive behavioral therapy (CBT) is an effective treatment for SAD.    4    Given it's still an emerging therapy, research on it remains inconsistent with other treatments.

Aside from seeking professional help, there are a couple of other things that people can do to help them cope with SAD during their day.     5    The researchers of the study had participants either go for a daily one-hour outdoor walk or use a low-dose artificial light box for 30 minutes per day for a period of one week. The participants who went for a daily walk showed significant improvements in all depressive symptoms, compared to those exposed to artificial light.

A．Colder weather and less daylight may have you feeling a bit more down lately.

B．Research also shows that lifestyle factors can play an important role in both causing and managing depression.

C．According to one study, getting more natural light during the day may help improve symptoms.

D．Of course, there may be other factors at play too.

E．But this doesn’t mean that there aren't many things people can do during the winter months to help them cope with their symptoms.

F．While these feelings may be temporary for some, around one in three people consistently struggle through the autumn and winter months.

G．Light therapy is also currently being investigated as a treatment for SAD.

2 . Foreseeing a time when a patient's own cells may be harvested, multiplied, and fashioned into a replacement organ, researchers in Boston have successfully transplanted laboratory grown bladders (肾) into six dogs.

For a century, physicians have replaced diseased or damaged bladders by removing sections of a person's intestines (肠子）and shaping them into a substitute bladder. While the procedure offers some relief to patients, complications often develop because nature designs intestinal tissue for a purpose-absorbing nutrients-other than holding waste liquid of the body. “You start absorbing stuff that should be removed," says Anthony Atala of the Children's Hospital in Boston.

Other physicians have turned to human-made materials to create artificial bladders, but those efforts have also run into problems. Consequently, to build a better bladder, Atala and his colleagues decided to employ the organ's own cells.

To turn the cells into an organ, the researchers first form plastic which can break down naturally into bladder-shaped shell. They then coat its outside and inside with layers of cells needed.

To test this strategy, Atala's group obtained bladder tissue from dogs and grew it into organs. After removing the dogs' bladders, the investigators implanted(移植）the artificial ones coming from the dogs' own cells. Within a month, the organs began to perform like normal bladders.

Within three months, the plastic shells had broken down naturally, and the implanted organs were hard to distinguish from natural ones, Blood vessels(血管） quickly grew into them. Moreover, nerves seem to form proper connections with the new organs, allowing the dogs to regain normal control of their bladders. Some dogs have had the artificial bladders for nearly a year without any problems nearly a year without any problems.

While the bladders of dogs closely resemble those of people, Atala warns that more testing of this transplant strategy must occur before artificial bladders are ready for the clinic.

1. The traditional method of shaping parts of intestines into a substitute bladder ________.

A．allows the patient to absorb useless things

B．brings the patient a lot of sufferings

C．prevents the patient from absorbing nutrients

D．worsens both the function of the intestines and the bladder

2. The artificial bladders implanted in dogs ________.

A．worked perfectly as long as three months

B．began to work as well as a normal one in a few weeks

C．proved to be able to work for several years

D．did not work properly until after a month

3. Why is it suggested that more testing should be made?

A．What suits dogs' bladders will also suit human bladders.

B．Dogs' bladders can be implanted into human bodies.

C．Human bladders may well be different from dogs.

D．Artificial bladders grown in dogs can be used for human beings

4. What does the passage mainly talk about?

A．The way of turning intestines into bladders.

B．The prospect of manufacturing plastic bladders.

C．The history of making artificial bladders.

D．The possibility of making bladders from their own cells.