Can someone please answer this because I have no clue and I’ve been waiting two hours for an answer

Because there are multiple of each elements provided also known as a chain or "continuation"

Explanation:

H-9

O-2

C-3

N-4

If it is shown as a ring, the ring will be composed of one oxygen atom, all the rest being carbons. All the carbon atoms will have OH groups except one of the carbon atoms attached to the ring oxygen. That same carbon atom may have a continuation of the carbon chain attached (e.g., a CH2OH group or a CH(OH)CH2OH group).

c

explanation:

the most common type of reef is the fringing reef. this type of reef grows seaward directly from the shore. they form borders along the shoreline and surrounding islands.