The plural possessive of kangaroo is kangaroos'.
No, kangaroos is a common, concrete noun, the plural form of the singular kangaroo. A collective noun is a word for a group of things; the collective nouns for kangaroos are a troop of kangaroos or a mob of kangaroos.
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 for the noun coyote is coyote's.
The possessive form is grandson's.
The possessive form is island's.
The possessive noun of Sam is Sam's.