Read the following statements w.r.t cellular respiration and select the correct option.
A. The breaking of C-C bonds of complex compounds through oxidation always occurs in the absence of oxygen.
B. All the energy present in respiratory substrate is not released free into the cells.
C. Energy is released in a series of slow stepwise reactions in enzymes.
D. The energy released by breakdown of C-C bonds is not used directly for cell metabolism.

• A

  Only (A) and (B) are correct.

• B

  (A),(B) and (D) are correct.

• C

  (B),(C) and (D) are correct.

• D

  (A),(B),(C) and (D) all are correct.