Please help me (wrong answers get reported)

Explain what will happen if decomposers were apsent from a forest ecoysystem.

Efficiency is the ratio of to for a system a)power in to power in b)power in to power out c) power out to power out d) power out to power in

Both speed and velocity measure how fast something is moving. however, since speed is not a it does not require a(n question 6 options: a) quantity , unit b) magnitude, unit c) scalar, direction d) vector, direction