Jamie grinds his teeth at night, so his dentist suggested wearing a mouth guard. After wearing the mouth guard for two weeks Jamie noticed that his jaw no longer hurt during the day. About two weeks later, Jaime’s parents received a call from the dentist’s billing department, who indicated that their insurance did not cover the cost of the mouth guard. A __________ effect is that Jaime’s jaw no longer hurts during the day. A ___________ effect is that his parents’ health insurance did not cover the cost of the mouth guard.
a.+; -
b.-; +
c.-,-
d.+,+