Goldfish don't know _______ to them three seconds ago.
A:what happens
B:what is happening
C:what happen
D:what happened
鸦片战争之后,古老的中华文明逐步被列强推了半殖民地半封建社会的深渊,日益走向开放的时代,对比晚清和新中国的对外开放,不同的是晚清的对外开放( )
现在国家决定停止开发“北大荒”的原因是( )