Pollution has many causes and can affect the air and water quality in a variety of ways. Nitrates are a common pollutant found in agricultural runoff. Four groups of students designed experiments to determine the effect of nitrates on algae growth. Which group of students designed an experiment whose variables would lead to the most valid results? Group 1 varied both the temperature and the amount of nitrates.
Group 2 kept both the temperature and the amount of nitrates constant.
Group 3 kept the temperature constant and varied the amount of nitrates.
Group 4 varied the temperature and kept the amount of nitrates constant.

the tides are influenced by both the moon and the sun, it's easy to see that when the sun lines up with the moon and the earth, as during a new moon or full moon, the tidal effect is increased. these are known as spring tides, named not for the season, but for the fact that the water "springs" higher than normal. on the other hand, if the sun and the moon are 90 degrees apart in relation to an observer on earth as during the first quarter moon or third quarter moon, then high tides are not as high as they normally would be. this is because despite its greater distance, the sun's mass allows it to exert enough gravitational force on the oceans that it can negate some of the effects of the moon's pull. this phenomenon of lower high tides is called a neap tide. if you need more information on this topic visit moonconnection.com.