Answered

Which is the best correction of the sentence fragment? Jill wants to get a new dress. Or a skirt.

AJill wants to get. A skirt or a new dress.
BJill wants to get a new dress, or she wants to get a skirt.
CJill wants to get a new dress or a skirt.
DJill wants to get a new skirt. Or a dress.

Verified Answer :

Your answer would be c. Because none of the others make sense. 
Jill wants to get. A skirt or a new dress uses improper punctuation
Jill wants to get a new dress, or she wants to get a skirt  Doesn't sound right.
And 
Jill wants to get a new skirt. Or a dress uses improper punctation

the correct answer is B because since its talking about either one you want a coma