Answer:
organ level
Explanation: because multiple types of tissues are working together.
The main purpose of hemoglobin is the transport of OXYGEN and CARBON DIOXIDE
I swear it's the cell membrane.. I'm not sure though
Answer: Hydrogen bonds.
Explanation: This seems like more of a chemistry question, but basically hydrogen bonding is way stronger than any other kinds of bonding, and because water molecules are all hydrogen bonded, they cling together a bunch and are thus super cohesive.
