Inner mitochondrial membrane has

The correct option is All of the above.

To understand why this option is correct, let us examine the structure and function of the inner mitochondrial membrane (IMM) and its role in the Electron Transport Chain (ETC):

The inner mitochondrial membrane is highly folded into structures called cristae, which vastly increase its surface area. This membrane is the site of oxidative phosphorylation and contains a series of protein complexes that transport electrons. These complexes are:

1. NADH dehydrogenase complex (Complex I): This is the first enzyme complex in the respiratory chain. It accepts electrons from NADH (generated in the citric acid cycle and other pathways) and transfers them to ubiquinone (coenzyme Q). During this process, protons are pumped from the matrix to the intermembrane space.
Therefore, the NADH dehydrogenase complex is located in the inner mitochondrial membrane.

2. b-c₁ complex (Complex III, or Coenzyme Q : Cytochrome c Oxidoreductase): This complex receives electrons from reduced ubiquinone (ubiquinol) and passes them to cytochrome c. This electron transfer is also coupled with the translocation of protons across the inner mitochondrial membrane.
Therefore, the b-c₁ complex is located in the inner mitochondrial membrane.

3. Cytochrome oxidase complex (Complex IV): This is the final enzyme complex in the electron transport chain. It receives electrons from cytochrome c and transfers them to molecular oxygen (O₂), reducing it to form water (H₂O). Protons are also pumped across the membrane by this complex.
Therefore, the cytochrome oxidase complex is located in the inner mitochondrial membrane.

Since all three complexes (NADH dehydrogenase complex, b-c₁ complex, and cytochrome oxidase complex) are integral components of the electron transport chain located in the inner mitochondrial membrane, the correct choice is indeed All of the above.