－Have you seen Mr. Black these days Jack?－Yes I met him when I in the street yesterday.

问题补充：

－Have you seen Mr. Black these days, Jack?

－Yes, I met him when I in the street yesterday.

A. walked

B. was walking

C. have walked

D. is walking

答案：

A. walked

(答案→)B. was walking

C. have walked

D. is walking

解析：句意：这些天你有看见布莱克先生吗，杰克？是的，当我昨天正在街道上走着时，遇到他了。用过去进行时表示动作正在进行，故选B