Select an example of an open system.
a.) earth
b.) the atmosphere
c.) the water cycle

answer is a

explanation:

b brown mice / white sand dunes

there is not 1 highest source of protein, but there are many; meats, fish, poultry, seafood, cheese, eggs, yogurt and milk. the only non complete animal food that is beneficial is gelatin.

sorry if this did not , have a great day!