If a Microsoft January 20 Put Option with a Strike

If a Microsoft January 20 put option with a strike price of $20 were about to expire and the market price of the underlying Microsoft stock was $15.00, the price of the put option would have to be __________ to eliminate arbitrage opportunities.

A) $1.00
B) $2.00
C) $4.00
D) $6.00
E) none of the above.