题目

Mrs. Smith has two children now. She tries to keep thin and never eats any meat or eggs. She likes all kinds of nice clothes. Mr. Smith has to spend much money on them .But the man always wears old clothes. He has not enough money to buy new clothes. Mrs. Smith hopes to keep young. She doesn’t want others to know how old she is.It was snowing heavily one afternoon. The head of her office went to a meeting. The woman had nothing to do. So she began to tell Mr.Smith about her birthday party. Mr. Smith works in the same office.“ You should have seen（真该看看） the cake,” said the wom某同学想通过实验来探究“影响滑轮组的机械效率的因素”．他做了如图所示的实验，并测算了各次实验装置的机械效率．关于他的实验过程，下列说法中不正确的是（ ）A．根据①、②两次实验可知：滑轮组的机械效率与绳子的绕法无关B．根据②、③两次实验可知：同一滑轮组提起物重越大，机械效率越低C．根据该同学的探究结论可知，通过适当增大物重可以提高滑轮组的机械效率D．为使实验的结论更具可靠性，应换用不同的装置进行多次实验归纳得出普遍规律