A scrub jay can remember when it
cached a particular place, researchers have discovered,and tend
not to bother to recover a perishable treat if stored long enough to have rotted.
i-tend not to bother to recover a perishable treat if
ii-they tend not to bother recovering a perishable treat
iii-tending not to bother to recover a perishable treat it
iv-tends not to bother recovering a persihable treat
v-tends not bothering to recover a perishable treat it
The subject verb agreement is tested here .The scrub is singular and hence it should be tends (singular) and not tend.
Only iv and v satisfy this condition.Option iv is idiomatically better .
+1 if you like my explanation .Thanks