Which of the following best describes a bull call spread?

Select one:

a$.$ Buying a call option with a lower strike price and selling a call option with a higher strike price

b$.$ Buying a call option and a put option with the same strike price

c$.$ Selling a call option with a lower strike price and buying a call option with a higher strike price

d$.$ Buying a put option with a lower strike price and selling a put option with a higher strike price