Possibly, but not necessarily. Except for a few fossil forms, such as the -s marker of the third person singular indicative and the present system of to be there is no number in the English verb.
The possessive singular noun is explorer's. The possessive plural noun is explorers'.
The possessive form for the noun coyote is coyote's.
The possessive form of zoo is zoo's.
The possessive form for the noun preacher is preacher's.
The possessive form for the noun laboratory is laboratory's.
No, he is not possessive. The possessive form would be his.
The possessive form for the noun oxygen is oxygen's.
The possessive form is grandson's.
The possessive form is island's.
The possessive form for the noun coyote is coyote's.
No, it is a singular possessive noun.
The possessive noun of Sam is Sam's.