题目

____ is known to us all is that the old worker, for _____ life was hard in the past, still works hard in his seventies. A.As; whom               B.What; whose           C.It; whose                D.What; whom 答案：B大气中的臭氧层能吸收来自太阳辐射的紫外线，保护地球上的生物．有关臭氧（O3）的下列说法中，错误的是（ ）A．臭氧和氧气互为同素异形体B．每个臭氧分子中有3个氧原子C．臭氧中氧元素以化合态存在D．臭氧由氧元素组成