根据句意和汉语注释,写出单词的正确形式。
小题1:The mid-term exam will be held ________ (大约) the middle of November this year.
小题2:Did you take the ________ (药) this morning, Mary? You look ill.
小题3:The old man couldn’t remember the ________ (领导) name, but he was really grateful to him.
小题4:Hiking in Qomolangma (珠穆朗玛峰) is the ________ (费力的) walk all over the world.