What does it mean that the vice president is "only a heartbeat away" from the presidency?

Newspaper started by john campbell:

The controlled use of fire by hominids: (a) limited the expansion of hominids into certain environments, such as dry grasslands. (b) decreased the amount of food energy available in the hominid diet. (c) contributed to geographical expansion and food production techniques in positive ways. (d) has been shown to contribute little to the digestive process of hominids.

Which of the following is a sign of a weak economywhich of the following is a sign of a weak economy