The number of species living in an ecosystem is referred to as?

Acceleration is a direct result of a.) balanced forces b.) unbalanced forces c.) gravity d.) velocity

Explain the source of radioactivity in uranium in earth’s crust by which it produces nuclear radiation

How much time has elapsed from the very beginning of "the memior of the conquistador bernal diaz del castillo" to the end? a. castillo's whole life b. a quarter of an hour c. a few weeks d. a decade