根据句意和汉语注释，在横线上，写出单词的正确形式。
Egypt is one of the most_________（古老的）countries in the world.
I am lucky because I have friends to share my sadness and _____________ (忧愁，不悦) with.
So far only a few countries have _____________ (成功)sent people into space.
He _______ (怀疑) if he would learn anything new from Marie when he was at school.