What is common between photosynthesis and respiration?

Cytochrome is related to

How many complexes are involved in the electron transport system $(ETS)$ in mitochondria?

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.

The last electron acceptor in respiration is

Chemiosmotic theory of $ATP$ synthesis in the mitochondrion is based on