The health condition of Yaya, a 23-year-old giant panda who has lived in Memphis Zoo in the US for 20 years, attracted public concern recently. Tourists posted pictures of Yaya and claimed she suffered from skin disease and malnutrition,    1    (call) for her return. With it being decided that Yaya will come back home, this episode raises the question of    2    giant pandas are so difficult to feed and breed.

Giant pandas only feed on bamboo. The Calgary Zoo in Canada sent two pandas back to China in 2020 due to a    3    (short) of bamboo. Pandas also have trouble absorbing nutrients. They can only digest 17 percent of what they eat.

Their low reproductive rate is a crucial reason as well.    4    (general), giant pandas can breed when they reach 4 to 8 years old. Females breeding only once    5    year leave their scent on bamboo so that males can locate them. Even if a pair meets, successful breeding is not certain.

Females normally give birth    6    one or two cubs(幼崽). If twins are born, the mother may only raise the    7    (strong) of the cubs. A newborn panda baby only    8    (weigh) about 0.1 percent of the weight of a fully    9    (grow) panda, making its survival extremely difficult.

Despite these    10    (issue), progress has been made in breeding and protecting the widely loved animals.

Over the last 20 years, the koala population in New South Wales     1     (fall) by 25 percent. About 36,000 koalas remain. As part of its plan, the government of New South Wales is setting aside nearly 25,000 hectares of forest, where koalas will be able to live freely. It will also add more signs     2     (help) car drivers avoid koalas that walk into roadways. And the state will build     3     (special) made bridges so that koalas and other wildlife can cross roads while     4     (avoid) cars and trucks.

Anne Hidalgo, the mayor of Paris, wants to clean the Seine,     1    (make) the river swimmable by 2024 when the city will host the Olympic Games. Unfortunately, the Seine has a lot of pollution, which is the addition of harmful materials     2     the environment. Around 360 tons of plastic     3    (find) in the Seine every year.

Lucky for Hidalgo, 11-year-old Raphael is on the case. For nearly two years, he     4    (spend) nearly every weekend with his dad, fishing debris (垃圾) out of almost     5     whole stretch of water. It all started when Raphael saw a YouTube tutorial from someone doing something similar. So Raphael asked his parents for     6     (supply). “I was initially taken back by his request.    7    , once he showed me the YouTube video I ended up being quite impressed,” Raphael’s dad said.

Raphael feels     8    (encourage) by his progress in the last two years. A section of the Seine, he said, is noticeably     9    (clear) than the rest of the river. That’s     10     he started fishing and he hopes he’ll be one of the first to swim in the water once it’s declared safe.

Important as face masks(口罩)are in our current world, they have a major impact on     1    environment. Now scientists have demonstrated a novel method for     2     (clear) away old masks—by using them     3     (make) batteries.

First, the researchers disinfect(给......消毒)the masks, then put them into a special liquid. Next, the masks     4     (press) together and heated to 140℃, forming small conductive balls that work as the electrodes(电极)of a battery. These are separated by a layer     5     is also made of old masks, then the whole thing is put into an electrolyte (a liquid that allows electricity to pass through it) and     6     (final) covered in a protective shell. The shell is made of a different type     7     medical waste—drug blister packs.

Of course, cleaning up face masks     8     (be) only part of the issue, and it wouldn’t be much help if the batteries weren’t any good. But the team claims that they’re surprisingly     9     (success). The best—performing version of the battery continues to have 82 percent of its power after 1,500 cycles, and can deliver energy for more than 10 hours.

The team says that these batteries have a number of other     10     (benefit) too. Using waste products means they’re low—cost, and they can be made thin and flexible.