Recent studies have shown that most US graduates receive cash as gifts, though the amountreceived ______ from person to person. [ ]

下列各句中，没有语病的一项是（ ）

The job isn’t challenging enough for me. I want something more ________.

Many people believe we will suffer from more environmental disasters _____we change the way we live[ ]

s warn that medical waste from hospitals, if properly, may contribute to spreading diseases