涛涛 GWD 9-14

Q14:

A scrub jay can remember when it cached a particular piece of food in a particular place, researchers have discovered, and tend not to bother to recover a perishable treat if
                stored long enough to have rotted.

1. tend not to bother to recover a perishable treat if
2. they tend not to bother recovering a perishable treat
3. tending not to bother to recover a perishable treat it
4. tends not to bother recovering a perishable treat
5. tends not bothering to recover a perishable treat it           答案D  想请问tends的主词是什麽   还有B为什麽错     谢谢前辈的指教