A
(2019·长春质检)Can exercise during childhood protect you against memory loss many decades later？Exercise early in life seems to have lifelong benefits for the brain，in rats at least.
“This is an animal study，but it shows that physical activity at a young age is very important—not just for physical development，but for the whole lifelong track of cognitive(认知的) development during aging，”says Martin Wojtowicz of the University of Toronto，Canada.“In humans，it may delay the appearance of Alzheimer's disease(阿尔茨海默病)，possibly to the point of preventing it.”
Wojtowicz's team divided 80 young male rats into two equal groups，and placed running wheels in the cages of one group for a period of six weeks.Around four months later—when the rats had reached middle age—the team taught all the rats to connect an electric shock with being in a specific box.When placed in the box，they froze with fear.
Two weeks later，the team tested the rats in three situations：exactly the same box in the same room，the same box with the room arranged differently，and a completely different box in a different room.
The rats without access to a running wheel when they were young now froze the same percentage of times in each of these situations，suggesting they couldn't remember which one was dangerous.But those that had been able to run in their youth froze 40 to 50 percent less in both changed box settings.
“The results suggest the amount of physical activity when we're young，at least for rats，has influence on the brain and cognitive health—in the form of better memories—when we're older，”says Arthur Kramer of Northeastern University in Boston，who has found that，in humans，exercise promotes the growth of new brain cells.
【语篇解读】 本文为说明文，介绍了一项科学研究，从而得出早期锻炼对大脑终生有好处的结论。
1．The study shows that .
A．physical activity is important for physical health
B．using the running wheels is of benefit to the rats' growth
C．physical activity can prevent humans' Alzheimer's disease
D．the more exercise a rat has when young，the better memory it will possess when older
D [细节理解题。根据第一段内容尤其是第二句“Exercise early in life seems to have lifelong benefits for the brain，in rats at least”可知，早期锻炼似乎对大脑终生有好处，至少对老鼠来说是这样的。故选D项。]
2．How are Paragraphs 3 and 4 mainly developed?
A．By analyzing causes.
B．By giving an example.
C．By describing the process.
D．By showing differences.
C [写作手法题。根据第三段的“Wojtowicz's team divided 80 young male rats into two equal groups...Around four months later...they froze with fear”和第四段的“Two weeks later，the team tested the rats in three situations”可知，本文第三、四段描述了Wojtowicz的研究小组对老鼠进行实验的过程。C项意为“通过描述过程”，故选C项。]
3．What does the underlined word“it”in Paragraph 2 refer to?
A．Exercise. B．Development.
C．Benefit. D．Study.
A [代词指代题。根据第二段的“but it shows that physical activity at a young age is very important”及“In humans，it may delay the appearance of Alzheimer's disease(阿尔茨海默病)”可知，身体活动很重要，对人类来说，它可能会推迟阿尔茨海默病的出现。因此“it”在文中指的是“physical activity”，A项与其同义，故选A项。]
4．What is the author's attitude towards the animal study?
A．Negative. B．Objective.
C．Critical. D．Doubtful.
B [观点态度题。通读全文可知，作者介绍了对老鼠进行实验的过程及其结果，并引用数据进行说明，由此可知作者对动物研究的态度是很客观的。B项意为“客观的”，故选B项。]
