The workers ___ busily when the boss came to look for something she ___ in the office.

A.had worked; had left   B. were working; had left  C. working; had left  D. had worked; left

The workers _____busily when the boss came to look for something she ______in the office.

  A had worked, had left   B were working ; had left  C working ; had left  D had worked; left

The workers ________ busily when the boss came to look for something she ________ in the office.

[　　]

A. had worked, had left 　　　　　　　　　　　　    B. were working, had left

C. working, had left 　　　　　　　　　　　　  D. had worked, left

The workers ________ busily when the boss came to look for something she ________ in the office.

[　　]

A．had worked; had left　　　　 B．working; had left

C．were working; had eft　　　　D．had worked; left