20．We met _____ and have become good friends since then.
| A．by mistake | B．by accident | C．by ourselves | D．by the way |
Canada is one of _____ largest countries in the world, ______ second only to Russia．
| A．the; the | B．the; a |
| C．a; the | D．the; 不填 |
The telephone _____ three times in the last hour, and each time it _____ for my sister.
| A．had rung; was | B．has rung; was | C．rang; has been | D．has been ringing; is |
Everyone knows that Canada is the second largest country in the world, larger than _____ country in Asia.
| A．any | B．any other | C．other | D．another |
By all _____, you must try every _____ to help him.
| A．mean; mean | B．means; means | C．means; mean | D．mean; means |
Before he was arrested, he had taken _____ one-month holiday, and stayed in the country with _____ 18-year-old girl, one of his colleagues.
| A．a; a | B．an; an | C．an; a | D．a; an |