下列计算正确的是（   ）

如果调查的范围很大，不可能逐个调查，就要选取一部分调查对象作为____ ，调查过程中要如实____ ．

Sarah: Hi, friends! My parents will have a birthday party for me.

Amy: Great! When is your birthday?

Sarah: It's on May 12th. It's my eleventh birthday. Will you come?

Amy: Yes！What about you, John?

John: What day is your birthday?

Sarah: It's Saturday. We have no classes.

John: OK. I'll come. Do you like sports?

Sarah: Yes, I do. I like playing football very much.

John: Good! I'll give you a surprising gift.

黄土高原东起____ ，西到____ ，北抵____ ，南连____ ，是世界上____ 的高原。