Henry' s job was to examine cars which crossed the frontier to make sure【C1】______they wer

e not smuggling(走私)anything into the country. Every evening except at weekends, he【C2】______see a factory worker coming up the hill towards the frontier, pushing a bicycle with a big load of old straw on it. When the bicycle【C3】______the frontier, Henry used to stop the man and【C4】______him take the straw off and【C5】______it. Then he would examine the straw【C6】______carefully to see whether he could find anything, and after that he would look in all the man's pockets【C7】______he let him tie the straw again. The man would then put it back on his bicycle and【C8】______down the hill with it.【C9】______Henry was always expecting to find gold or jewelry or other【C10】______things hidden in the straw, he never found【C11】______, even though he examined, but he was not【C12】______to imagine what it could be.

Then one evening, after he had looked【C13】______the straw and emptied the factory worker's pockets【C14】______, he【C15】______to him, "Listen, I know that you【C16】______things across this frontier. Won't you tell me what it is that you're【C17】______into the country so successfully？ I'm an old man, and today's my last day on the【C18】______. Tomorrow I 'm going to retire. I【C19】______that I shall not tell anyone if you have been smuggling." The factory worker did not say anything【C20】______some time. Then he smiled, turned to Henry and said quickly, "Bicycles."

【C1】

A．if

B．unless

C．whether

D．that