Certain corals have been found in extremely deep water. These coral lack the zooxanthellae that are found in tropical coral reefs because zooxanthellae require sunlight to go through photosynthesis and there is no sunlight available at these depths. These deepwater coral often are built upwards instead of across the bottom. Why do the polyps build the coral this way?

a.)The pressure of the deep water is too great to build outwards.
b.)They grow to avoid predators.
c.)They are filter feeders.
d.)The temperature of the water keeps them from building outwards.

Question

Certain corals have been found in extremely deep water. These coral lack the zooxanthellae that are found in tropical coral reefs because zooxanthellae require sunlight to go through photosynthesis and there is no sunlight available at these depths. These deepwater coral often are built upwards instead of across the bottom. Why do the polyps build the coral this way?  

    a.)The pressure of the deep water is too great to build outwards.
    b.)They grow to avoid predators.
    c.)They are filter feeders.
    d.)The temperature of the water keeps them from building outwards.