The United States of America _____one ofthe most developed countries in the world.

When you are reading English novels, if you meet with some new words you can this dictionary. Which of the following can’t be used in this sentence?

－She looks very happy. She ___________the exam.－I guess so. It’s not difficult after all.

I don’t think he will come to our party, _____?

I am wondering ________ my invitation and join me for the trip to Hainan this summer.