Which part of the male reproductive system is at particular risk after middle age? (1 O urethra
vas deferens
O prostate
O epididymis

The organ of the male reproductive system that is particularly at risk after middle age is the prostate.

Explanation:

The prostate is a gland found in connection with the urethra and the urinary bladder and is part of the male reproductive system. It is responsible for secreting substances and promoting the output of semen through the urinary channel, during ejaculation.

In middle age, after 40 to 45 years of age, it is possible to see problems related to the prostate, such as benign prostatic hyperplasia and less frequently prostatic adenocarcinoma. The infection, called prostatitis, usually occur relatively frequently and are related to urinary tract infections or some sexually transmitted diseases.

Regarding other options:

    Urethra , vas deferens  and epididymis are part of the genitourinary system, and are subject to other pathologies, especially infectious, which can occur at any time in the life of man.

when you rub, you also apply pressure, that pressure can urge the poop to come out. i think that when your rubbing, you also might be slightly breaking it up and that can further fill the stomach.  

i believe it is true.