题目

So busy _____ that he has no time to see a film．        A．was he                                       B．he was          C．is he              D．he is 答案：C 密度计是利用___________________原理来测量_________的仪器。如图，同一支密度计分别放置在甲、乙两种液体里均静止不动，则密度计在两种液体中所受的浮力F甲 _____F两种液体的密度ρ甲  ______ρ乙。（选填“＞”、“＜”或“＝” ）