题目

We haven’t enough books for everyone; some of you will have to _____.     A. help                        B. enjoy     C. share                       D. spare 答案：C 如图，⊙O1与⊙O2的半径分别为R＝8，R＝4r，圆心距O1O2＝12，若用皮带把两圆连接起来，求皮带的长．