19.The prices of goods kept ____. We had to cut the expenses in order to meet our daily needs.
| A．standing up | B．breaking down | C．going up | D．putting up |
At last, the boys found themselves in a pleasant park with trees providing shade and_________down to eat their picnic lunch.
| A．to sit | B．sat | C．sitting | D．having sat |
The researehers delermine what type of plants the virus can infect(感染) and_________insects can carry the virus.
| A．those | B．why | C．which | D．how |
—Did you get my letter?
—I received one just as I_________.
| A．set out | B．had set out | C．was setting out | D．would set out |
．When she called at his studio, she_________that he had gone to Japan.
| A．is told | B．was told | C．tells | D．told |
．Robert made a call to his parents yesterday afternoon. To his disappointment, _________of them answered it.
| A．either | B．both | C．none | D．neither |