As a new graduate，he doesn't know ________it takes to start a business here.
| A．how | B．what | C．when | D．which |
21．The moment we heard the news of the earthquake, we began to ________ the work to rescue those who were trapped in the building.
| A．set off | B．set down | C．set aside | D．set about |
20. When Jane began to take swimming lessons, her main__________was the fear of water.
| A．evidence | B．crisis | C．obstacle | D．Danger |
19. The language used in advertisements differs from____________used in ordinary readings.
| A．which | B．what | C．that | D．It |
18._________is often the case, he didn’t study hard and failed to pass the test.
| A．What | B．Which | C．It | D．As |
17.They had a pleasant chat____________a cup of coffee.
| A．for | B．with | C．during | D．Over |