Question

what are the possesive and the plural possesive forms of the following words:

shelf
wrench
bus

Thank You

Answer 1

These are all semi-regular nouns. They're not completely irregular (i.e., child, man, woman, ox, etc.), but they don't form plurals by simply adding -s.

Think of each noun, regular or irregular, as having four forms:

desk (s), desk's (s. poss.)
desks (pl), desks' (pl. poss.)

So ... I'll do the first one for you:

shelf, shelf's
shelves, shelves'

Now ... how will you write the other three forms of the other two? If you're not sure, be sure to use a dictionary to find the plural -- http://www.dictionary.com