How many corals are dead in the Caribbean? ​

over 50 percent of the world's coral reefs have died in the last 30 years and up to 90 percent may die within the next century—very few pristine coral reefs still exist. The impact of our changing climate on coral reefs was manifested by the third global bleaching event in 2015/16.

Explanation:

a symbiotic relationship with the mitochondria

b tumor cells have a cell wall instead of a membrane

explanation:

tumor cells different from normal cells because tumor cells have a cell wall instead of a membrane.