Have you ever noticed that your fingertips are winked when you’ve just finished swimming or washing dishes? It seems as if your hands have aged 30 years in a second. But is this an accident? Or is it something that nature has built into our bodies?
If your finger’s wrinkling up had no use at all, “ it wouldn’t need to.” Professor Tom Smulders from Newcastle University, UK, told BBC News. By studying wet fingers closely, Smulders and his partners found that the wrinkles looked a bit like the patterns on the car tire or on the bottom of the running shoes. So they made a guess that wrinkles on fingers might be able to help the hand hold things more tightly.
To test this, researchers asked 20 people to pick up marbles from water with their hands. But before they started, some of the people had to keep their hands in water for half an hour.
The researchers found that the people with wrinkled fingers completed the task the task faster than those with dry hands. But when they were asked to move dry marbles, all the people performed equally well, no matter they had the wrinkled fingers or not.
Our ancestors might not have played with marbles, but wrinkled fingers could have made it easier for them to climb around in the wet forests and catch fish from rivers, researchers say.
Similarly, our toes also get wrinkled in water. This may have developed from our ancestor’s need to run on wet ground.
But the question is, if wrinkled fingers are so helpful, why don’t our hands just stay that way all the time? Researchers explained that wrinkling has its disadvantage: wet fingertips are far less sensitive than smooth ones, reducing our sense of touch.
What does the underlined world “this ” in the third paragraph refer to?

A．Whether fingers have wrinkles after they are put in water.

B．Whether wrinkled fingers can hold things more tightly.

C．Why keeping things in water makes them wrinkled.

D．Why wrinkles help hands hold things more tightly.

The test shows that ________.

A．winkled hands hold dry things more tightly than dry hands do.

B．dry hands hold dry things more tightly than wrinkled hands do.

C．winkled hands hold wet things more tightly than dry hands do.

D．dry hands hold wet things more tightly than wrinkled hands do.

What might be the disadvantage of wrinkled fingers?

A．They are too sensitive to be touched.

B．They might be more likely to get hurt.

C．They cannot hold things tightly enough.

D．They are not so sensitive as dry fingers.