So the Li is oxidized and the F is reduced.
when you become negative you gain electrons=reduction
The atom that causes the reduction is the reducing agent, so since the Li caused the F to be reduced it is the reducing agent.And vice versa. The F is the oxidizing agent.
B) Fe is oxidized, but the element that is reduced is Cu.The charge must change for it to be oxidized or reduced.The SO4 is -2 the whole time.Fe is the reducing agent and Cu is the oxidizing agent.
Whatever is oxidized is the reducing agent, and whatever is reduced is the oxidizing agent.