Is a system of rules that tells us what we can and cannot do?

What was the main purpose of one of the first world organizations

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.

Nami conducts an investigation on plants. she places a grow light on a timer to give the plants different amounts of light to see if this would affect their growth. in this investigation, the amount of light is the .