Yeah, I realized that mistake after I made the key. (For what it's worth, when I was grading, I gave points to either answer)
If that were on a test though, I would answer attacking other colonies, simply because it is simply one of many methods by which coral filter feed, while they are the principal way they attack other colonies. If that does come up on another test, you may want to politely let the proctor know.
Sorry for any confusion.
Life List: n. A list of bird species definitively seen by a birdwatcher.
PacificGoldenPlover's Life List : 319
Most recent lifer: Red-throated Loon
2014 (Mira Loma/Troy/Regionals/States/Nationals)
Dynamic Planet (2/2/1/1/1)
Designer Genes (1/4/1/13 (???)/13 (figures)
Water Quality (1/1/3/1/3)