How much of the Earth's atmosphere do scientists believe was made of oxygen 2.3 billion years ago?

A.) 70%

B.) 22%

C.) 1%

D.) 10%

Why do plants at the bottom of a pond grow better than the plants at the bottom of a lake

The Europe's second longest river forms a border between Romania and before it drains into the Sea.

Which of the following is FALSE? A) Venus has a density of 5.2 grams per cubic centimeterB) All Terrestrial planets have densities much higher than the density of waterC) The density of Jupiter is 1.

What is a benefit of using renewable energy resources?

What does it mean to adapt to a new climate? A. to leave one climate and travel to another B. to change behaviors in order to meet a climate's challenges C. to change from one species to another because of the climate D.

What are the most wide spread Paleozoic fossils?

Less developed nations are to extended families as more developed nations are to nuclear families. matrilineal families. families of procreation.

If star a has an apparent magnitude of - 6 and star b has an apparent magnitude of 5, which star is brighter in our sky?

What is one advantage of free trade?

Explain how the shading of the direct light of the sun causes a lunar eclipse.