Which corrects any error in the use of apostrophes in the sentence?

My little sister sometimes writes her letter b's backwards.

A.
backward's

B.
bs

C.
writes'

D.
There is no error in this sentence.

I think D.

Question

Which corrects any error in the use of apostrophes in the sentence? 

My little sister sometimes writes her letter b's backwards.
 
 A.
backward's
 
 B.
bs
 
 C.
writes'
 
 D.
There is no error in this sentence.

I think D.

conqueror · Answer

You're right.

king.void. · Answer

yes : D

anonymous · Answer

Thanks ^_^ sorry it took me so long i was doing something else

king.void. · Answer

$$\huge \color {pink} {No, problem :D} $$