Q.Which is the correct order of action ?

The correct regulatory chain is LH stimulating the Leydig cells to secrete testosterone, which in turn drives spermatogenesis.

In the male reproductive (HPG) axis, LH released from the anterior pituitary acts specifically on the Leydig cells (interstitial cells) of the testis, stimulating them to synthesise and secrete testosterone (androgen); testosterone then acts on the seminiferous tubules to stimulate spermatogenesis. (FSH, separately, acts on Sertoli cells, stimulating secretion of factors like ABP that support spermatogenesis, and inhibin from Sertoli cells feeds back to suppress FSH.) Option (a) wrongly places Inhibin between LH and spermatogenesis and omits testosterone/Leydig cells from the correct pathway. Option (c) is wrong because TSH is thyroid-stimulating hormone, which regulates thyroid function, not spermatogenesis, and it does not act on Sertoli cells. Option (d) wrongly uses LTH (luteotropic hormone/prolactin, involved in …