The general at last got a chance to visit the village_________he used to fight, _________he had been dreaming of for years.

A．that; which

B．where; that

C．in which; what

D．where; which

对于可逆反应2SO₂+O₂⇌2SO₃，在混合气体中充入一定量的¹⁸O₂，足够长的时间后，¹⁸O原子（　　）

A．只存在于O₂中

B．只存在于O₂和SO₃中

C．只存在于O₂和SO₂中

D．存在于O₂、SO₂和SO₃中