需求
参考答案：
把所有可能的价格与需求量之间的对应关系称为需求。
下述哪项不会减少钴-60几何半影（）
A、钴源直径少
B、源皮距缩短
C、源限距加长
D、照射野缩小
E、肿瘤深度浅
.In an effort to maintain social balance, the Chinese government several years ago _______a policy of encouraging college graduates to take official positions in rural areas.
A．adapted
B．adjusted
C．adopted
D．admitted
