Question

–How long has John _______?

–For almost eight months.

1. A.
   become an engineer
2. B.
   stayed in Beijing
3. C.
   joined the music club
4. D.
   bought the CD player

Answer 1

B
how long 要与延续性动词连用，故选B，只有选项B为延续性动词，其余都不是。