country in 2050.

His father looksyoung, but in fact he is ______.

I’m sorry I forgot theletter for you! I’m really busy these days”—It doesn’t matter, I’ll post it myself.”

He looks very happy. He ____have passed the exam, —I guess so. It’s not difficult after all.

It is said that the gravity on Mars is only about __________ of the gravity on earth．