Which sentence contains an incorrect possessive form?

a.

his solution took everybody's objections into account.

b.

it looks as though that calf has wandered away from its mother.

c.

the credit for the decorations is all hers'.

d.

someone's bike is in the driveway.

pls me its 11pm and i gotta pass before 12am

but, i think its either d or c.