What is the number of chromosomes in a human sperm cell?

Which of the following is an artificial method of vegetative propagation?

Which of the following sexually transmitted diseases is caused by a virus?

$(a)$ Identify the organisms $A$ and $B$ and the mode of asexual reproduction exhibited by them.
$(b)$ How will an organism be benefitted if it reproduces through spores?
$(c)$ Mention the two asexual methods by which Hydra can reproduce. Explain briefly any one such method.

$A$ part of the male reproductive system is shown below. Study the diagram and answer the questions that follow.
$(a)$ Two parts have been incorrectly labelled. Identify them.
$(b)$ Give the function of urethra.
$(c)$ Which hormone is released by testis?

Which among the following diseases is not sexually transmitted?