The amount of matter that cycles through a food web
a) stays constant.
b) continually increases.
c) continually decreases.
d) changes unpredictably.

Option A, stays constant.

Explanation:

The matter and energy with is a given food web or ecosystem remains constant. It just get transferred from one trophic level to other in varied amount but in totality the amount of energy and matter produced at the starting of the food chain remains same. However, the energy transferred at each trophic level is only 10% of its previous trophic level.  

Hence, option A is correct

sound moves fastest in solids because the molecules are tightly packed and it allows sound to vibrate

1)

i))the process of preparing food by green plants in the presence of sunlight is called photosynthesis.

ii) leaf is the site for photosynthesis.

iii) it takes place as,

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