Hi, Zuoping. Welcome to the Forum. The first is correct.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
ZuopingI know the first one is correct but why ? Robert is singular so shouldn't all verb include s or es ?When an auxiliary verb (like "do") is used, the main verb does not change.
ZuopingRobert is singular so shouldn't all verb include s or es ?No. Only one verb in a sequence is allowed to have s or es, and it has to be the first in the sequence unless that's a modal verb, in which case none of the verbs in the sequence have s or es.