Make sure you have prepared everything well before you the plan. A. try on B. break down C. think of D. carry out 答案:D 【解析】考查动词短语辨析。句意:在你实施计划之前确保一切都已经准备好了。Try on“试穿”;break down“出故障”;think of“想起”;carry out“执行,实施”。计划应该是用来执行的,故选D。等质量的下列物质在相同条件下体积最大的是 ( )A.H2B.O2C.N2D.CO2