Consider the following statements : (i) The sex of a child is determined by what it inherits from the mother. (ii) The sex of a child is determined by what it inherits from the father. (iii) The probability of having a male child is more than that of a female child. (iv) The sex of a child is determined at the time of fertilisation when male and female gametes fuse to form a zygote. The correct statements are :

In humans, sex determination is genetic.

• Statement (i) is incorrect because mothers have two $X$ chromosomes ($XX$) and always contribute an $X$ chromosome to the child.
• Statement (ii) is correct because fathers have one $X$ and one $Y$ chromosome ($XY$). The sex of the child depends on whether the sperm carrying an $X$ or a $Y$ chromosome fertilises the egg.
• Statement (iii) is incorrect because there is a $50\%$ (1:1) probability of having either a male or a female child.
• Statement (iv) is correct because the sex is determined at the moment of fertilisation when the sperm (male gamete) fuses with the ovum (female gamete) to form a zygote.