Scenario an Abundant and Continual Supply of ATP Is Necessary for Necessary

Scenario
An abundant and continual supply of ATP is necessary for all living cells. Toxins, reduced blood flow, and a compromised respiratory system can interfere with the transport of oxygen to active cells. A runner in a marathon faces multiple obstacles to continue to produce sufficient ATP to remain competitive.
-When the circulatory system cannot deliver oxygen fast enough to support a runner's aerobic metabolism, cells switch to an emergency mode in which ________.

A) ATP is generated less efficiently by harvesting the heat energy in a cell
B) ATP is inefficiently produced and lactic acid is generated as a by-product
C) lactic acid is broken down to produce smaller amounts of ATP
D) carbon dioxide is joined with water to generate much smaller amounts of ATP