(1) An increase in stock price causes an increase in the value of a call option. (2) An increase in exercise price causes a decrease in the value of a call option. (3) An increase in the time to expiration causes an increase in the value of a call option. (4) An increase in the risk-free rate causes an increase in the value of a call option. (1) An increase in the variance of stock return causes an increase in the value of a call option.