I ate sandwich while I was waiting for 20:08 train.A. the; aB. the ;theC. a; theD. a; a

I ate sandwich while I was waiting for 20:08 train.
A. the; a
B. the ;the
C. a; the
D. a; a

A. the; aB. the ;the(答案→)C. a; theD. a; a解析：考察冠词。句意；当我正在等20:08的火车期间吃了一个三明治结合语境可知前文是泛指任何一个三明治，故用不定冠词。下文特指八点零八分的火车，用定冠词。故选C.

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