Answer:
The most effective experimental approach to assess the effects of elephant impact on vegetation is to assess plant responses under differences in elephant density. It is important that other factors, such as soils or habitat structure are held constant so that the only factor which varies is elephant density.
Explanation:
source: Studying Elephants icun.org
Answer: the first one
Explanation: the rest are very wasteful :)
ANSWER:
Needed to form cell membranes
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