The word “rusty” in the third paragraph means _________

Câu hỏi: Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 46 to 50. onsinn
It's often said that we learn things at the wrong time. University students frequently do the minimum of work because they're crazy about a good social life instead. Children often scream before their piano practice because it's so boring. They have to be given gold stars and medals to be persuaded to swim, or have to be bribed to take exams. But the story is different when you're older.
Over the years, I've done my share of adult learning. At 30, I went to a college and did courses in History and English. It was an amazing experience. For starters, I was paying, so there was no reason to be late – I was the one frowning and drumming my fingers if the tutor was late, not the other way round. Indeed, if I could persuade him to linger for an extra five minutes, it was a bonus, not a nuisance. I wasn't
frightened to ask questions, and homework was a pleasure not a pain. When I passed an exam, I had passed it for me and me alone, not for my parents or my teachers. The satisfaction I got was entirely personal.
Some people fear going back to school because they worry that their brains have got rusty. But the joy is that, although some parts have rusted up, your brain has learnt all kinds of other things since you were young. It has learnt to think independently and flexibly and is much better at relating one thing to another. What you lose in the rust department, you gain in the maturity department.
In some ways, age is a positive plus. For instance, when you're older, you get less frustrated. Experience has told you that, if you're calm and simply do something carefully again and again, eventually you'll get the hang of it. The confidence you have in other areas – from being able to drive a car, perhaps – means that if you can't, say, build a chair instantly, you don't, like a child, want to destroy your first pathetic attempts. Maturity tells you that you will, with application, eventually get there.
I hated piano lessons at school, but I was good at music. And coming back to it, with a teacher who could explain why certain exercises were useful and with musical concepts that, at the age of ten, I could never grasp, was magical. Initially, I did feel a bit strange, thumping out a piece that I'd played for my school exams, with just as little comprehension of what the composer intended as I'd had all those years before. But soon, complex emotions that I never knew poured out from my fingers, and suddenly I could understand why practice makes perfect.
The word "rusty" in the third paragraph means _________
A. staying alive and becoming more active
B. covered with rust and not as good as it used to be
C. impatient because of having nothing to do
D. not as good as it used to be through lack of practice