Let's see -
We can try to rewrite the sentence twice, each with one of the verbs. Then, read each one aloud and see which one sounds better. This is a really helpful method when looking at subject-verb agreement.
→ Few people eat enough leafy vegetables
→ Few people eats enough leafy vegetables
In this case, A) eat is the correct answer.
↑ ↑ ↑ Hope this helps! :D
