Which final cytochrome in the respiratory chain donates electrons to oxygen?

Given below are two statements.
Statement-$I$: Cytochrome $c$ is a small, copper-containing protein loosely attached to the inner membrane.
Statement-$II$: Cytochrome $c$ acts as a mobile electron carrier transferring electrons between complex $I$, $II$, and $IV$.
In the light of the above statements, choose the correct answer from the options given below.

What is ubiquinol?

In which stage of cellular respiration is the maximum number of $ATP$ molecules produced from $ADP$ through the complete oxidation of glucose?

Which of the following contains both iron and copper?

In the electron transport system in the inner mitochondrial membrane,complex-$I$ and $IV$ are respectively: