题目

下列说法中正确的是（    ） A．物质发生化学反应时不一定都伴随着能量变化 B．反应热只与反应体系的始态和终态有关，而与反应的途径无关 C．放热反应不需要加热就一定能发生 D．伴有能量变化的变化都是化学变化 答案：B He is clever, but is never good at his lessons, which suggests that he ________． [　　] A．should be very hard working B．should be hard working enough C．is very hard working D．isn’t hard working enough