题型:选择题 某人估测一竖直枯井深度,从井口静止释放一石头并开始计时,经2s听到石头落地声.由此可知井深约为(不计声音传播时间,重力加速度g取10m/s2)( )A.10 mB.20 mC.30 mD.40 m 查看答案
题型:选择题 — _____, Tom,Where's my doll? — Oh, sorry, I don't know. I think _____ behind the door. [ ]A. Excuse me, it's B. Here you are, she's C. I'm sorry, its D. How are you, he's 查看答案