"鹳鱼石斧图彩陶缸"属于我国新石器时代的（）。 A.龙山文化 B.仰韶文化 C.马家

It was _____ computer games that cost the boy a lot of time that he ought to have spent on his lessons.

A．to have played

B．playing

C．played

D．having played

何谓瞳孔调节反射?

儿童生长发育的速度是直线上升的，而且各系统的发育也是均衡的。

以随机访问方式读取文件中的数据通常使用istream的成员函数______。

妊娠12周以前，尿液经多少倍稀释后，如HCG胶乳凝集抑制试验仍呈阳性反应，可怀疑葡萄胎( )

A．100
B．200
C．300
D．250
E．500