The most important thing about cotton in history is ___part that it played in ____Industrial Revolution.
| A．/,/ | B．the,/ | C．the , the | D．a ,the |
With such an ecological variety, amazing natural beauty, and so much to do, it's _______ that the falls are a wonder.
| A．no doubt | B．no way | C．no wonder | D．no problem |
Having finished the work, _______.
| A．it was almost six o’clock |
| B．supper was ready |
| C．a postman came and delivered some letters. |
| D．we had a rest and then had supper |
---When was Tom bitten by a snake?
---It was on a Sunday _______ he was taking a trip to the mountainous area.
| A．that | B．when | C．which | D．where. |
When this new kind of virus broke out at first in Mexico, no one had the least idea that it would _______ so rapidly throughout the world.
| A．export | B．spread | C．expand | D．deliver |
---Is the new job a real challenge for him?
---Well, _______ difficulties he meets，I believe he will never lose heart.
| A．however | B．whenever | C．whatever | D．Whichever |