题目

完形填空Double Trouble When I was eight, I wanted a toy and needed $10 to buy it. But, as usual, I was broken. I decided to ask my 11-year-old sister, Kathleen, for a loan. I went to her room1her for the cash. Laughing, she agreed to2me the money, but added, “I will charge you 10 percent compound interest every 3until you pay me back.” “Compound interest what's that?” I asked. “Well, interest is what you call the4money borrowers have to pay back on a loan,” she explained. “Compound interest means that the interest payments get bigger and bigger the5you take to pay back the lo一列向右传播的横波在t=0时的波形如图所示，A、B两质点间距为8m，B、C两质点在平衡位置的间距为3m，当t=1s时，质点C恰好通过平衡位置，该波的波速可能为（ ） A. B. 3m/sC. 13m/sD. 27m/s