题目

.  _______ US newspaper reported, that from next autumn, ________ new computer system will follow the progress of international students at their schools in the USA. A. 不填; a          B. The; the                               C. A; a                    D. A; 不填   答案：C下列有关原子结构及元素周期律的叙述正确的是A．同主族元素的原子最外层电子数相同，化学性质也相同 B．同周期元素(除0族元素外)从左到右，原子半径逐渐减小 C．第ⅦA族元素从上到下，其氢化物的稳定性逐渐增强 D．同主族元素从上到下，单质的熔点逐渐降低