Cells are to tissues as tissues are a. systems b. molecules c. organs d. system

I would say organs, since cells are the main function of tissues. Tissues are the main function or organs, so I believe that c. is the correct answer.

Have a great day :) Let me know if there is anything else you need!

coral.

explanation:

coral. many marine organisms that produce calcium carbonate shells or skeletons are negatively impacted by increasing co2 levels and decreasing ph in seawater.

i'm assuming that the correct answer is indeed the first one/ "a"..