Radioactive isotopes are used to
a.
determine the absolute age of rocks.
c.
determine how rocks are formed.
b.
determine the relative age of rocks.
d.
determine how rocks are changed.

Mosses, lichens and shrubs can be found where in russia? a.grasslands b.mountain regions c.coastal plains d.siberian tundra

Fertility and mortality rates are higher in more developed nations.

Which ecosystem best fits the characteristics listed below? which ecosystem best fits the characteristics listed below? ii. seasonal migrations of millions of wildebeests, zebras, and elephants iii. large numbers of predators, such as lions iv. acacia trees and grasses a. the congo rainforest b. the african mangroves c. the serengeti grasslands d. the sahel