依次填入下列各句横线处的成语，最恰当的一组是（ ）①大量外国游客涌入中国， ，可能会导致犯罪率的提高。②中国高等教育用不到十年时间实现了从精英教育到大众教育的历史性跨越，但在大反战的过程中，难免会 ，出现各种各样的问题。③这些 的野山人参，是用萝卜根制作的。④他虽说是个大学生，但没什么专长，现在仍然只是给别人打打工， 的，真替他担心。

upposed to clean the room, but it is still in a mess. —Oh, I was so busy that I forgot.

My parents asked me ______ my sister with herschoolwork.

You ______ be hungry already, you had lunch only two hours ago! [ ]

The jet fighters were waiting at the airfield, ________ radar searching the sky