A、During the childhood. B、In the middle age. C、At the old stage. D、Throughout life. D

M: But don’t many more parents live apart from their married children than used to be the case?
W: True, but this is because many more young families can afford to own their own homes these days than ever before. In other words, parents and their married children usually live in separate households because they prefer it that way, not because the children refuse to have mum and dad living with them.
M: Is this a good thing, do you think?
W: I think that it’s an excellent arrangement. We all like to keep part of our lives private, even from those we love dearly. I certainly don’t think that it’s a sign of the increased loneliness of old age.
M: Are people’s mental abilities affected by old age?
W: Certain changes do take place as we grow older, but this happens throughout life. These changes are very gradual and happen at different times with different people, but, in general, if you know a person well in his middle age and have seen how he deals with events and problems, you will easily recognize him in old age.
M: So that someone who enjoys new experiences, travel, education, and so on in his middle years will usually continue to do so into old age?
W: Exactly. We have carried out some very interesting experiments in which a group of people aged 60-70 and a group aged 30-40 had to learn the same things. The first thing we discovered was that the young group tended to be quicker at learning than the old group. However, although the old group took longer to learn, eventually, they performed as well as the young group. And when we tested the two groups several weeks later, there was again no difference between the two groups.
M: That’s very interesting indeed. What else did your experiments show?
W: Well, one group of old people agreed to attend evening classes for a year to study English and mathematics. In fact, most of this group became so interested in their studies that they continued them for another year. Anyway, we discovered that they did best in the English classes and that most of them steadily improved their ability to communicate in both the written and the spoken language.
M: What about the group who studied mathematics?
W: Well, that’s a different story. There seems to be no doubt that people find maths more difficult as they grow older. Though why this is so, I cannot say.
M: Perhaps pocket calculators will solve this problem.
W: I think you’re right. In fact, I’m sure that you are.
M: Okay. Time for a commercial. Stay tuned: we’ll be right back.
6. Why are there more parents living apart from their married children now?
7. What’s Professor McKay’s attitude towards more parents living apart from their children?
8. When are people’s mental abilities affected by age?
9. What did Professor McKay’s interesting experiments find?
10. What can’t Professor McKay offer explanation for?