A varicocele is an abnormal enlargement of veins in the pampiniform plexus which may hinder blood flow through the pampiniform venous plexus into the testicular vein. The reduced venous drainage and the resulting elevated testicular temperature may be caused by .
a. defective venous valves in the testis
b. elevated systemic arterial blood pressure
c. elevated core body temperature
d. reduced testicular arterial blood flow

the correct answer is (a) defective venous valves in the testis

Explanation:

Varicocele is found to be caused by defective venous valves in the veins within scrotum.This venous valve is called the pampiniform venous plexus. It is network of small veins, that surrounds each testicular artery.In addition to its function in venous return from the testis,it also plays a role in the thermal regulation of the testis. It reduces the temperature by absorbing heat from the arterial blood, cooling it before it enters testis.

Hence statement (a) is the correct answer.

tsd is temerature dependent sex determination.

tsd: it is a type of environmental sex determination in which the temperature experienced during embryonic/ larval development (ambient temperature for development) determine the sex of the offspring.

crocodile displays the tsd where the ambient temperature of the developing egg determines the individual's sex. for example in the american alligator's eggs, incubation at 33 ºc produces mostly males, while incubation at 30 ºc produces mostly females. so if the american alligator's egg will get the ambient temperature (33 degree celcius)during embryonic development from egg, the offspring will be male and same for the female sex determination.