When Brianna tries to start her new car and the motor stalls, she gets out of her car and screams that she will sell the car to anyone for $$10.$ Nelly, a passerby who owns Nelly's Used Cars, hands Brianna $$10.$ This is

a$.$

$$not a valid acceptance because Nelly is only passing by$.$

b$.$

$$a valid acceptance because Nelly is a professional dealer.

c$.$

$$not a valid acceptance because Brianna does not seriously intend to sell.

d$.$

$$a valid acceptance because Brianna is seriously frustrated.