How many days of sunlight are in the aquatic ecosystem?

How many variables are altered in a good experiment? a.1 b.0 c.2 d.3

Need the diagram below, which is not drawn to scale, shows the position of the earth, moon, and sun. what type of eclipse occurs when the earth, moon, and sun are lined up in the order shown? a. planetary eclipse b. solar eclipse c. martian eclipse d. lunar eclipse

What is any method of measuring the age of an object or event in years, such as using atomic half-life?