2. Which systems (2) are directly involved in the digestions (mechanical and chemical) of food?
3.
Which systems (2) control responses to internal and external environments?

2. liver, pancreas oesophagus.

3. cells specifically receptors, and effectors ( not sure)

they float because they are less dense than the water itself

something denser than water, like a rock, will sink to the bottom

the correct answer in apex is tissue development, i know because i just had this question