In case of a Bull Spread, which one of the following is not incorrect?

Choose one:

a.When the strike price of the call option sold is equal to the stock price, then the total payoff is also zero.

b.It involves buying a European call option on a stock with a certain strike price and selling an American call option on the same stock with a higher strike price.

c.Both options have different expiration dates.

d.When the strike price of the call option sold is lower thanthe stock price, then the total payoff is zero.

e.When the stock price is higher than the strike price of the call option sold, then the total payoff cannot be negative.