Healthy corals are brightly colored because they . secrete colorful pigments to protect themselves from ultraviolet light secrete colorful pigments to attract mates build their skeletons from colorful minerals host symbionts with colorful photosynthetic pigments

The best answer is "D"

"host symbionts with colorful photosynthetic pigments."

Explanation:

A symbionts is an organism that is very closely associated with another usually prolonged. This is an act of symbiotic living where they both benefit from each other at different level.

Corals have a mutual existance with micoralgea symbionts known as zooxanthellae. They provide food for the coral and in return the coral plant provide them with accomodations and nutrients.

The correct answer is D: "host symbionts with colorful photosynthetic pigments"

Explanation:

Healthy corals are brightly colored because they host symbionts with colorful photosynthetic pigments

Corals are translucid or white. They can host different organisms that live on and among them, giving place to an amazing ecosystem.

One of these organisms is the photosynthetic unicellular microalgae, called zooxanteles, that are colorful and provide nutrients to the coral.

When changes in radiation, temperature or salinity in water occur, corals react to these changes losing these algae and becoming translucid again.    

option c is the correct answer.

for example, no new evidence will demonstrate that the earth does not orbit around the sun (heliocentric theory), or that living things are not made of cells (cell theory), that matter is not composed of atoms, or that the surface of the earth is not divided into solid plates that have moved over geological timescales .