hello,
here is your answer:
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Multicellular organisms are made up of millions of cells. These cells are divided into separate groups. Each group performs a specific function. Since these cells carry out only a particular function, they do it efficiently.
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hope this helped,
:)
They can enter your blood stream (via breathing/ingesting) and once in your bloodstream they can enter cells and mutate your dna, which can cause cancer/birth defects/ reproductive harm
Trees in the rainforest are so tall because they compete for sunlight. Hope this helps!
It is the first one, prevents sperm from reaching the egg and fertilizing it :) (made fairly obvious in the question where it states they are blocked/severed.)