EARTH'S PROTECTIVE SHIELD. Earth is surrounded by invisible gases that form a thin protective blanket that we call the atmosphere. It contains the oxygen that we breath as well as other important gases such as nitrogen, carbon dioxide, water vapor, and ozone.
Answer:
B-B. Gymnosperms are placed among Dicotyledons
The answer is C. The original population is the dotted line and the population after the selection is the faded blue. The two shell patterns are increasing while the most common was is decreasing.
Nitrogen, I found my answer here
http://slideplayer.com/slide/8953264/
