Asphyxia is a condition caused by which of the following?

Asphyxia is primarily characterized by insufficient oxygen reaching the body's tissues, which often occurs in conjunction with an increase in carbon dioxide levels in the blood. This imbalance can result from various factors, including respiratory distress, obstruction, or other conditions that inhibit proper breathing.

When oxygen levels decrease and carbon dioxide levels increase, the body's ability to function properly is severely compromised, leading to symptoms such as confusion, loss of consciousness, and potentially death if not addressed promptly. Option B accurately describes this critical scenario, emphasizing both the lack of oxygen and the presence of excess carbon dioxide, which are fundamental to understanding asphyxia.

Other choices may touch on relevant aspects of respiratory function but do not capture the duality of low oxygen and high carbon dioxide that is central to the definition of asphyxia.