Most multicellular organisms are composed of cells with different shapes and sizes, and those cells perform different functions. what
is the best explanation for this?

Which element provides strength to the exoskeleton of clams and oysters

The large increase in atmospheric carbon dioxide in the last 50 years most likely comes from a. an increase in cellular respiration b. increased decomposition by bacteria c. an increase in the burning of fossil fuels d. an increase in photosynthesis

Can someone i have no idea of how to do this.