71. John has really got the job because he showed me the official letter ________ him on it.
A. offered B. offering C. to offer D. to be offered
72. Mathematics ________ the language of science.
A. are B. was C. is D. is to be
73. I went to the school ________ my father once worked.
A. that B. which C. where D. on which
【解析】考查定语从句关系词。此句先行词the school，定语从句my father once worked，二者构成的完整句为my father once worked in the school. “in the school”是一个地点状语，故选C。
74. It was not until 1920 ________ regular radio broadcasts began.
A. which B. when C. that D. since
75. No one failed in the exam, ________?
A. was he B. did one C. did they D. didn’t he
【解析】考查反义疑问句。当主句主语是one, everybody, anyone, somebody, nobody, no one等不定代词时，疑问部分常用复数they或者单数he。前面是否定，后面用肯定，排除D，故选C。