Which of the following describes a difference between a warrant and an exchange-traded option?

a. In a warrant issue the firm is the guarantor while for an exchange-traded option the clearinghouse is the guarantor

b. The number of exchange-traded options is fixed whereas the number of warrants in existence depends on trading

c. Exchange-traded options unlike warrants have a single strike price

d. Warrants unlike exchange-traded options cannot be traded after they have been purchased