5 . Americans spend billions on vitamins, multivitamins for their health, but a review of numerous studies concluded there is little to no evidence that some of those vitamins prevent heart disease, cancer or death.

The report, released by the U.S. Preventive Services Task Force last week, concluded that “recent evidence is not enough” to determine whether vitamins actually help or hurt your health, based on 84 studies, 52 of which were done since 2014. Vitamins examined included vitamins A, B, C, D and E, as well as other multivitamins.

“Our suggestion is neither for nor against taking vitamins, or combinations of those nutrients (营养物质). We just don’t have enough evidence,” said Dr. John Wong, a doctor in the Department of Medicine at Tufts Medical Center who was involved in the report.

While the finding is that vitamins don’t have any benefits to “healthy, non-pregnant (未怀孕) adults”, it doesn’t apply to “children, people who are pregnant or may become pregnant, or people who are hospitalized.”

The Task Force admitted it makes sense that people would take vitamins in hopes of health benefits, as some shortage may lead to illness. But experts agreed the best way to get good health and prevent cancer is a balanced diet and regular physical activity.

“The suggestion across all organizations about vitamins is to eat a balanced diet, and then the key tends to be on plenty of fruit and vegetables and less junk foods,” Wong said.

Wong added people should refer to their health doctors to determine if any vitamins are worth taking. He said this suggestion should also serve as a need to further research into proving the official benefits and risks for each vitamin.

9 . Steph Clemence always intended to go to college. But life has a(an) _________ throughout her early childhood years to _________ barriers. Growing up, she led a nomadic (漫游的) life because her mother, who remarried several times, was always on the _________. By the time of high school, Steph had lived in 25 places.

When her stepfather died in a car accident, leaving her mother to support three daughters on a(an) _________ income, paying for college became a serious question. But she still tried to figure out what to do with a life so _________ her plan for schooling.

The _________ came one afternoon when she was cleaning her bedroom. She _________ a thick document where she found a handout titled “Mrs. Clark’s Book List” by her high school English teacher Dorothy Clark.

It wasn’t homework, but it could be a(an) _________ for those not able to receive higher education due to _________ problems like her. The teacher had spent months creating a list of 153 books whose contents would be as __________ as a two-year study at an arts college.

Steph studied the list. Each of those books __________ her to learn more. The reading list was also a(an) __________ in her everyday life, even __________ with her on vacations to find out the next book. She never did get to college, but has now only four books left before __________ the list. She wishes she could thank Mrs. Clark for how reading the __________ on the list has changed her life.

10 . When I was a practice teacher in a middle school，the students in my class were always making ______，and had no interest in chemistry. So I decided to do ______to change their______ towards chemistry.

The evening before I would teach all by myself，I gave a piece of paper to everyone. I told them to write ______ they wanted on the paper and handed it in and then I could tell what each one had ______ .All the students said I _____ be longsighted(远视)．Then I stood ______ my back towards them. I didn't turn back ______ they had finished and ______ all the paper in a cardboard case.

I turned the cardboard case with the bottom(底部)towards the students，and told them calmly what each one had written on the paper. The students were surprised，______ that I had learned their ______ completely in such a short time.

I told them the truth and they were ______ at my brightness：there were five lines of students in the classroom，and every line had ten students. I had written serial number(from 1 to 50 )on every ______ of the paper in a chemical reagent(试剂)that cannot be seen ______eyes，and then gave ______out to the students according to the groups of their seats. After the paper was ______ in，I used______ chemical reagent onto the corner of the paper. Thus the serial number was ______！

______ ，the students became ______ interested in chemistry，and we became good friends.