The correct option is B spurious
The word 'genuine' refers to being truly what something is said to be.
Option A, imported refers to something brought from another country for sale.
Option B, spurious refers to something not being what it purports to be.
Option C, antique refers to belonging to ancient times.
Option D, duplicate refers to something exactly like something else.
Thus, according to the meaning, the word 'spurious' is the opposite of the word 'genuine'.