They are so close friends and their friendship ________ college days.
| A．dates back to | B．dates back | C．dates to | D．dates back from |
The book was written in 1946, __________ the education system has witnessed great charges.
| A．when | B．during which | C．since then | D．since when |
—Where did you get to know her?—It was on the farm __________ we worked.
| A．that | B．there | C．which | D．where |
Some pre-school children go to a day-care center, __________ they learn simple games and songs.
| A．then | B．there | C．while | D．where |
After graduation she reached a point in her career __________ she had to decide what to do.
| A．that | B．what | C．which | D．where |
We shouldn’t s0pent our money testing so many people, most of __________ are healthy.
| A．that | B．which | C．what&nze:1bsp; | D．whom |