Which has a greater buoyant force on it, a 35.0-cm3 piece of wood floating with part of its volume above water or a 35.0-cm3 piece of submerged iron?

The iron has, because it's displacing more water than the wood is.

diagram is missing, but i will try to explain your doubt.

answer:

amplitude is the maximum displacement or distance moved on a point of a vibrating body or wave measured from its equilibrium position.it is equal to half the length of vibration path.

answer; how far out of place which the object finished relative to the starting location;