The best answer is D, birds.
For more information and details on the way a bird's respiratory system works:
https://asknature.org/strategy/air-flow-patterns-facilitate-efficient-gas-exchange/
Octopus and squid have little suction cups on their tentacles. It helps with sticking onto food (so it doesn't get away) and also helps with sticking into things. If it wanted to camouflage into some rocks, it can use its tentacles to cling to to the rock.
Tentacles can also grab and carry things. Scientists have made tests where they would put a clam in a jar with the lid screwed on. The octopus would grab onto the jar and use its tentacles to twist the lid off.
Without tentacles, octopuses and squids would be pretty helpless and probably couldn't survive in the deep ocean.
Explanation:
Compounds are those substances that are made up of elements that are combined in a fixed proportion or ratio. The individual property of element is lost once it forms a compound. The physical and chemical properties of both compound and an element is different.
Example of a compound is water and its elements are hydrogen and oxygen. Water is a colorless liquid that acts as a solvent and dissolves most of the solutes in it. While oxygen and hydrogen occurs as gases in their elemental state.
From an area of high concentration to an area of low concentration.
