It seem like there are information missing on the question posted. Let me answer this question with all I know. So here is what I believe the answer is, the catalyst has acted upon it.
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This is where the exchange of gases , nutrients and waste occurs between the tissues and the blood due to the small pores and spaces are between the cells
Explanation: On Oct 12th, 2020 the largest expedition ever undertaken came to an end after researchers spent over a year studying climate change and ice drifting in the Arctic.
The stage that scientists begin to ask questions and attempt to explain observations is A. forming hypotheses. This is because a hypothesis is basically a testable question about observations scientists make.
