_The work is easy for an expert _______it is difficult for an inexperienced person.
| A．because | B．therefore |
| C．while | D．unless |
They desired that they _____ the right to vote.
| A．had | B．have | C．are | D．were |
As the boy listened attentively in class, everything his teacher said was easily______.
| A．for him to understand | B．understood | C．to understand | D．to be understood |
Mary is said _____ in the supermarket for 5 years, but I don’t know why she resigned last month.
| A．to have been working | B．work | C．to be working | D．to have worked |
______ from the space, you will find the earth is blue.
| A．Seen | B．Seeing | C．See | D．To see |
He was about to go out for a walk _____ his teacher came to visit him.
| A．while | B．which | C．when | D．then |