Fa boy exhibits a sex-linked trait that is carried on the x chromosome, what must be true?

If a boy exhibits a sex-linked trait that is carried on the X chromosomes, his mother carried at-least one allele for that trait. 
The boy has a X chromosome inherited from his mother and he inherited Y chromosome from his father. So, his mother must carried at least one allele for that trait because he exhibits a sex linked trait that is carried on X chromosome.

Photo means light and synthesis means combination so combination of light

C) to ensure each new cell has an exact copy of the dna