Which statement correctly describes the X Games? A. Events are strictly judged according to precise rules.
B. Games are held every four years.
O C. It is difficult to add or remove an event from the X Games.
D. The main events include BMX, snowboarding, and skateboarding.

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.