An American Option Can Best Be Defined As

An American option can best be defined as:

A) The right to buy an asset at a fixed price during a particular period of time.
B) The right to sell an asset at a fixed price during a particular period of time.
C) An option that can be exercised at any time until its expiration date.
D) An option that can be exercised only on the expiration date.
E) An option with payoffs in real goods.