Time ________ quickly. Three years passed before we knew it.
| A．went by | B．went on | C．went away | D．went off |
Mr. Smith is busy these days ________ a new book on how to develop a child’s reading skill.
| A．working out | B．working on | C．working for | D．working with |
It makes no ________ to me what she says. I won’t care.
| A．choice | B．efforts | C．difference | D．differences |
Who do you think is the right person to ________ the task?
| A．undergo | B．undertake | C．understand | D．underline |
He transplanted the young tree to the park ____it was the best time for it .
| A．where | B．when | C．what | D．that |