Mackey Corp. is incorporated in Delaware but has no office in the state. Its main office is in Arizona. Mackey would have a physical presence in Delaware to be sued in a case not involving an auto accident if____________.

a. it sells products to Delaware residents using the USPS for delivery.
b. it maintains a sales agent in Delaware.
c. it advertises its products in Delaware newspapers.
d. its sales personnel drive through Delaware to go to offices in Arizona.