--Did you see the traffic accident yesterday?

--Yes. It happened when I _________ past the museum.

1. A.
   walk
2. B.
   am walking
3. C.
   will walk
4. D.
   was walking

--- Did you see the traffic accident yesterday?

--- Yes. It happened when I ________ past the museum.

[　　]

(2005蘇州市)

--- Did you see the traffic accident yesterday?

--- Yes. It happened when I ________ past the museum.

[　　]