题目内容：

阅读理解。

One in five people carry a “smart gene” variant(变体)linked to long lifespan,bigger forebrains and enhanced mental ability,researchers have found.

“We’ve known for a long time that people lose cognitive(认知) abilities as they age,but now we’re beginning to understand that factors like KLOTHO can give people a boost in aging.Genetic variation in KLOTHO could help us predict brain health and find ways to protect people from the diseases that happen to us as we grow old,like Alzheimer’s disease(老年痴呆症),” said senior author,Dena Dubal of University of California.

The KLOTHO gene affects a protein found in the kidneys and the brain that regulates many different body processes.About one in five people carry a single copy of the variant,known as KL-VS,which boosts levels of the protein and is associated with a longer lifespan and improved heart and kidney function.A small minority,3% of the population,has two copies,which is linked to a shorter lifespan.

In the new study scientists scanned the brains of 422 men and women aged 53 and over who were also tested for the KLOTHO gene.They found that participants with a single copy of the gene variant also had a larger brain region known as RDLPFC,which is especially likely to shrink with age.Loss of neurons in this area may be one reason why older people are sometimes easily distracted and find it difficult to do more than one task at the same time.

Researcher Dr Jennifer Yokoyama said,“The brain region enhanced by genetic variation in KLOTHO is vulnerable(脆弱的)in aging and some mental disease.In this case,bigger size means better function.It will be important to determine whether the structure increase associated with carrying one copy of KL-VS can offset the cognitive(认知的)shortage caused by disease.”

People who have one copy of a variant KL-VS tend to live longer and have lower chances of suffering a stroke(中风),whereas people who have two copies may live shorter lives and have a higher risk of stroke.

1.What can we learn from the second paragraph?

A.People’s cognitive abilities do not decline if people have KLOTHO.

B.With the clear understanding of KLOTHO,Alzheimer’s disease can be cured now.

C.Genetic variation in KLOTHO could be helpful in treating mental disease in elderly people.

D.Genetic variation in KLOTHO could lead people to suffer from Alzheimer’s disease.

2.If a person carries two copies of the gene variant,he/she may    .

A.have better kidney function

B.have a shorter lifespan

C.have a higher level of the protein in his/her body

D.suffer from some cognitive disease

3.The reason why older people’s attention is easily distracted may be that    .

A.they have fewer neurons in the RDLPEC

B.their brain region is too large

C.they have two copies of the gene variant

D.they have more neurons in the RDLPEC

4.What does the underlined word “offset” in Paragraph 5 probably mean?

A.Prevent.           B.Balance.

C.Keep.             D.Promote.