After someone faints, smelling salts of ammonia may be placed under the person's nose. The person breathes the ammonia vapors, which deliver a sharp jolt to the nasal membranes, and the person wakes up. This illustrates:

Explanation:

Fainting is known as lipotimias, syncopes or presyncopes, when knowledge is not lost. They occur when not enough blood reaches the brain in a situation of transient hypotension, in which the regulatory mechanisms that redistribute blood to the brain to maintain oxygen fail. "It is the lack of cerebral percussion that causes the loss of consciousness producing hypotension that lasts a few seconds or minutes," as the expert points out.

Syncopes are generally benign, except for those with a cardiac cause, which are more violent syncopes of sudden death, in which the patient does not have time to react and loses consciousness completely.

The rest are the vasovagal or neuromediated syncopes, which represent a problem when the patient suffers them very frequently or if he falls and is hurting himself. The symptoms that are usually experienced when suffering from syncope can be: feeling of emptiness in the stomach and heat in the head, dizziness or instability and cold sweating.

answer; i believe that the best answer is (secondary cardiac arrest due to

d concave shape of wave rock

explanation:

the concave shape of wave rock is a very good evidence that supports the evolution of earth due to chemical weathering. if we talk about structure of   wave rock, studies have estimated that it is around 2.7 billion years old. it also serves as the foundation of evidence that it was the place where australian continent began to form.

how the structure of wave rock was created?

studies suggest that structure of wave rock was created when the surrounded area was started to weather due to which deposition of material started on the part of land which now contains wave rock.

the structure of wave rock is considered to be one of the best-known landforms in australia. at the height of around 15 cm, there can be found flared slopes which formulate the margins of hyden rock. it is now assumed by geologists that wave rock was created by subsurface water-induced weathering and not by glaciers, waves or wind.

due to deposition of material over the period of long time, the wave rock became tougher and tougher due to weathering from surrounding terrain. this makes it a physical evidence that supports   the evolution of earth due to chemical weathering.

hope it !