Which of the following is classified as a sign of hypocapnia?

Hypocapnia, which is a condition characterized by a reduced level of carbon dioxide (CO2) in the blood, can lead to various physiological effects due to changes in blood pH and oxygen delivery to tissues. One of the signs associated with hypocapnia is muscle tightness or spasms, primarily because low CO2 levels can lead to respiratory alkalosis, which in turn causes vasoconstriction and reduced blood flow to muscles. This can result in muscle cramps or spasms as the muscles do not receive adequate oxygen and nutrients.

While dizziness, numbness, and slight nausea can also be related to hypocapnia, muscle tightness and spasms are more directly indicative of the physiological changes occurring due to low CO2 levels, making it the more appropriate answer in the context of signs specifically linked to this condition.