There is no doubt that all this puts a large _________ on a teacher with a large number of classes.
17. The new outline will throw light _______ students’ understanding of history.
--- Well, Linda, I’m sorry but I have to leave.--- _______. I hope to hear from you soon.
15. Researchers _______ to develop vaccines and this will probably take several months to complete.
14. Water can absorb and give off a lot of heat, thus ________ a stable environment.
13. He took ________ advantage of cultural resouces and succeeded in ________ 1990s.