Answer:
refrain from using or disposing of (something); retain for future use.
Explanation:
The answer is C, Photosynthesis because it’s an non human activity, it’s energy from the sun
Answer:
A food chain outlines who eats whom. A food web is all of the food chains in an ecosystem.
Explanation:
Each organism in an ecosystem occupies a specific trophic level or position in the food chain or web.
Answer:
<u>Once the myosin-binding sites are exposed, and if sufficient ATP is present, myosin binds to actin to begin cross-bridge cycling. Then the sarcomere shortens and the muscle contracts. In the absence of calcium, this binding does not occur, so the presence of free calcium is an important regulator of muscle contraction.</u>
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