He failed to live up to ______ had been expected of him.
【正确答案】 A
【答案解析】解析：本题考查名词性从句。live up to(符合，达到预期标准，没辜负)后面没有宾语，可以判断是接了宾语从句，该宾语从句缺主语，只能用疑问代词what来引导宾语从句，故答案选A。