The fact that there are seasons on Earth is largely due to _______.

Comets in the solar system are believed to originate in either the Oort Cloud or the ______.

The cosmic microwave background radiation is the ___________________.

The octet rules states that atoms try to get ______ electrons in their outer shell.

The distance from the Earth to the sun in known as a(n) __________.

The findings from the Apollo space missions to the Moon support the idea that the Moon formed from the impact of Earth with a very large object.

Hard water generally contains significant amounts of which two ions? 

Which of the following elements is a metal?  

Jupiter’s Great Red Spot is presently believed to be ________.

A strong acid is a concentrated solution of the acid.