天然建筑材料勘探网（点）间距如何控制？
参考答案：
A={x||x-a|＜1}，B={x||x-2|＞3}，且A∩B=∅，则a的取值范围______．
He made a living ______ doing some important things. [ ]
A. with
B. in
C. to
D. by
