HE ………… WHEN I ………. IN, AND HE OBVIOUSLY ………. FOR A LONG TIME,BECA...

43. He ………… when I ………. in, and he obviously ………. for a long time,

because he ……….. very tired.

a. worked / came / had been working / was

b. was working / came / had been working / was

c. was working / came / has been working / was

d. worked / came / had worked / was

--> b