46.This morning in the class, our teacher lost his _______ at last because he could not stand any more.
47.It is not ---_______ for me to return all the books to the library now because I still need some of them for my research.
48.When traveling alone in the mountains, you’d better take a _______ with you in case you get lost.
49.As a teacher, you should not _______ the students from asking questions in class.
50.If you have any problems during your study here, please do not _______ to call me for help