Hi There!
Biotic factors are all the living things in an ecosystem, and abiotic factors are all of the non-living things in an ecosystem. So, they differ because they both mean opposite things.
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Answer:
a = (v2 - v1) / t
From A to B (8 - 4) m/s / 1 s = 4 m / s^2
From A to D ( 7 - 4) m/s / 5 s = .6 m / s^2
Note these equations hold for "uniform" values
They say nothing about the acceleration at intermediate points - the equation just says that his average speed increased from 4 m/s to 7 m/s during a 5 sec period
Small evidence is also called trace evidence.
The answer is either C or D..