Why do our hair become grey?

As we get older, the pigment cells in our hair follicles gradually die. When there are fewer pigment cells in a hair follicle, that strand of hair will no longer contain as much melanin and will become a more transparent color — like gray, silver, or white — as it grows.

Option D.

Step-by-step explanation:

we know that

To find the average speed divide the total distance by the total time

so