Answer:
(a) and (d) are correct
Explanation:
AIDS is a disease that's usually transmitted by sexual contact and breast feeding.
The answer is commensalism because the hermit crab doesn’t cause harm
Active transport moves molecules across the plasma membrane of a cell with the help of transport proteins and energy (ATP).
Active transport is the means of transport of molecules across the plasma membrane with the help of energy. This method is usually used for the transport of molecule against their concentration gradient, i.e., from lower concentration to higher concentration.
Plasma membrane is the outer layer surrounding the cell. It is made up of lipid bilayer, proteins, carbohydrates and cholesterol. The lipid bilayer is amphipathic since the lipid head is hydrophilic and its tail is hydrophobic. The plasma membrane is semi-permeable in nature.
To know more about active transport, here
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An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment, interacting as a system. ... By feeding on plants and on one-another, animals play an important role in the movement of matter and energy through the system.
Probably to not contaminate food or accidentally poison it.
