The answer is A, just took the test on edge
Receptors which provide animals with information from the external environment are located in ears, tongue, eyes, and the nose. These are all receptors that can be found in our sensory organs and provide us with feedback from our nearby environment and the stimuli on which we should be alerted towards.
The correct option is C.
When a dog is afraid, its ears are usually pinned back to the head. A dog showing aggression will pulled its ear up and forward.
Other signs that a dog shows when it is afraid include: lowering of the head, wrinkling of the nose, curled lips that show many teeth, tucked tail, panting, etc.
Signs show by an aggressive dog include: head held high, curled lips only show the front teeth, tail is upright and stiff, no panting, etc.
Bacteria that change nitrogen gas from the atmosphere into solid nitrogen usable by plants are called nitrogen-fixing bacteria. These bacteria are found both in the soil and in symbiotic relationships with plants.
Aminos acids are used to build proteins