It depends on whether you want the possessive form of porcupine (singular) or porcupines (plural) because there is a difference.
1. singular porcupine: just add an apostrophe followed by -s: porcupine's
2. plural porcupines: just add an apostrophe (not followed by -s): porcupines'
The correct answer is C. Because an antique is an old object.
Rosetta Stone is used to teach languages
