You needn’t take your shoes off when you enter someone’s house in Australia , _____ , of course , they’re very dirty .
| A．before | B．since | C．when | D．unless |
Do you consider _______any good attempting many scientific experiments?
| A．there | B．it | C．this | D．that |
I can’t help _______the house because I’m busy making a cake.
| A．to clean | B．cleaning | C．cleaned | D．being cleaned |
People couldn’t help _____the funny villager.
| A．laugh at | B．to laugh at | C．laughing at | D．laughing on |
She reached the top of the hill and stopped _____on a big rock by the side of the path.
| A．to have rested | B．resting | C．to rest | D．rest |
I can’t imagine _____that with such a famous author.
| A．work | B．to work | C．to be working | D．working |