(2)

Smaller Y chromosome does not decide the gender of the child. Its presence is important not the size. Thus, both assertion and reason are correct but reason is not the correct explanation of the assertion.

(3)

Male is responsible for the sex determination in humans because it has different kinds of chromosomes namely XY. A child which inherits X chromosome from his father will be a girl and the one who inherits Y chromosome will be a boy. Thus, assertion is true but reason is false.

(2)

Vegetative propagation involves using parts of the plant like stems, roots, or leaves to grow new plants. These plants are genetic clones of the parent and often reach maturity faster since they bypass the seedling stage. As a result, they can flower and potentially produce seeds earlier than seed-grown plants. Vegetative propagation is often used for plants that are difficult to grow from seeds, whether due to sterility or other factors.

(1)

Both the sperm and ovum have 23 pairs of chromosomes, so when the zygote is formed after their fusion it forms 46 chromosomes in the zygote, and hence the number of chromosomes is restored in the offspring. Thus, both assertion and reason are correct and reason is the correct explanation of the assertion.

(3)

Unisexual flowers are those which can have either stamen or carpels as sex organ. It is not true that it has only stamen in it. It can have only carpel also, so either of these will describe a unisexual flower. Thus, assertion is true but reason is false.

(4)

In angiosperms the female gametophyte is seated deep in the ovarian cavity, quite away from the stigma. In seed plants, the male gametes are brought to the egg containing female gametophyte by a pollen tube. A pollen grain does not pass down the stigma. Only its pollen tube does so. Thus, assertion is false but reason is true.

(3)

Ovulation takes place on the 14th day of the menstrual cycle, so if the sperm happens to meet the ovum during that phase fertilisation will take place. Thus, assertion is true but reason is false.

(1)

Semen (seminal fluid) contains the sperm cells as well as the seminal plasma. The seminal plasma is the secretion from the tubules of the seminal tract (seminal vesicles, etc) and from the seminiferous tubules in the testicles. It nourishes the sperm cells from ejaculation up to fertilisation. The vas deferens joins the ends of the seminal vesicles to form the ejaculatory ducts. Thus, both assertion and reason are true and reason is the correct explanation of assertion.

(2)

Human males have 2 testes and the testes descend into the scrotum just before the birth for the movement of the foetus in the canal. Thus, both assertion and reason are correct but reason is not the correct explanation of the assertion.

(1)

Lumen of Fallopian tube is lined by ciliated epithelium as Cilia have a rhythmic waving and beating motion that helps substances to travel from one place to another. Thus, both assertion and reason are correct and reason is the correct explanation of the assertion.