Most commonly used marker enzyme in clinical diagnosis of prostate cancer is

The correct option is D Acid phosphatase
Prostate cancer is the development of cancer in the prostate which is a gland in the male reproductive system. Prostatic acid phosphatase (PAP), also known as prostatic specific acid phosphatase (PSAP), is an enzyme produced by the prostate which is the most commonly used marker for the diagnosis of prostate cancer. It may be found in increased amounts in men who have prostate cancer or other diseases.

So, the correct answer is 'Acid phosphatase'.