Heredity is the process by which biological parents pass to their children.
a. traits
b. traditions
c. customs
d. culture

Traits! if the mom had blue eyes and blonde hair and the dad had brown eyes, brown hair, the child might have the traits of blue eyes and brown hair, or brown eyes and blonde hair, or even blue eyes, blonde hair, or brown eyes, brown hair. Parents pass their traits down to their kids, who then pass the traits they got down to their kids. the worlds an amazing place, ain't it?

Heredity is the process by which biological parents pass traits to their children.

Genes..
Hair color, lengths, grain
Eye color, size
Nose size
Skin tone
Voice.
And so on.