高级神经活动的基本过程有：（）。
A、兴奋和抑制
B、集中、扩散与相互诱导
C、条件与无条件反射
D、第一与第二信号系统
参考答案：A
煤气压力太低会发生（）现象。
A.脱火
B.回火
C.中毒
D.爆炸
Today, we'll discuss a number of cases ____ parents have much difficulty in communicating
with their children.[ ]
A. which
B. that
C. where
D. why
