There is no doubt that all this puts a large _________ on a teacher with a large number of classes.
| A．tax | B．catastrophe | C．sense | D．burden |
13. In any case, parents should make clear _______, if any thing, the children are expected to pay for with the money.
| A．that | B．which | C．what | D．How |
14. Many new games are designed on the computers all the time; people of all ages ______ these games.
| A．are playing | B．had played | C．have been playing | D．Play |
15. --- Who are the teenagers gathering at the school gate?
--- Well, if you _____ know, they are all my visiting students.
| A．need | B．must | C．may | D．Will |
16. Nothing taught by others can have the same effect on you as _____ learned by yourself.
| A．that | B．what | C．which | D．It |
17. In China, _______ bicycle is ______ popular means of transportation.
| A．the; a | B．a; / | C．the; the | D．a; the |