Trials.
Methods, control, and variables aren’t the experiments themselves.
Answer is combination
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Answer:
Due to its spreading nature.
Explanation:
Transboundary environmental threats like pollution is a problem for both parties i. e. one that is producing pollution and the other which is not producing it, because pollution can't remain at one place and spread from one part to another part of the earth due to open environment. So due to its spreading, it affected both the producing and non-producing parties.
A 5-carbon base, C,A,G,T are the 5 bases available