It was not until he came back ______ he knew the police were looking for him.
 
【正确答案】 C
【答案解析】 句意:直到他回来,他才知道警察正在找他。本句为“not...until...”句型的固定用法,It is(was)not until...+that...意为“直到……才……”。故本题选C。