题目

在化学反应：4HgS + 4CaO = 4Hg + 3CaS + X中，X的化学式为    A． SO2   B．SO3   C．CaSO3   D．CaSO4 答案：DYou can’t go to the mall with John,         he has got his driver’s license.A．even though B．because C．so D．if