不等式x-3＞2的解集为（ ）
A．x＞-1
B．x＜5
C．x＞5
D．x＞-5
x-3＞2，
x＞5，
故选C．
用化学符号表示下列意义：
（1）2个氢原子______；（2）3个钙离子______；（3）4个双氧水分子______．
I do homework every day, usually when I come ______ home ______ school. [ ]
A. to; from
B .at; for
C./ ; from
D. from; to
