题目

单项填空；从A、B、C和D四个选项中，选出可以填入空白处的最佳选项。 — Is David          honest and organized boy?   — Yes, that is why he was chosen to be the president of the Students’ Union.      A. a                             B. an                            C. the                           D. /某同学用如图所示的方法测量细钢丝的直径；将细钢丝在铅笔上紧密排绕32圈后用刻度尺测量，测得这个线圈的长度是    cm，细钢丝的直径是    mm．