Approximately how much fluid does the body lose per day in insensible perspiration?

Rationale:
A. Apocrine glands are located mainly in the axillae, groin, and around the nipples. They become active during puberty and secrete a thicker sweat that is more related to emotional stress, not temperature regulation.
B. Eccrine glands are the primary sweat glands responsible for thermoregulation. They are distributed widely across the body and secrete watery sweat, which cools the body through evaporation, making them the most important for maintaining core temperature.
C. Sebaceous glands secrete sebum (oil) that lubricates skin and hair but have no role in temperature control.
D. Endocrine glands secrete hormones into the bloodstream and regulate many processes (such as metabolism and growth), but they are not directly responsible for cooling the body through heat dissipation.

Rationale:
A. Lactic acid is a byproduct of anaerobic metabolism when oxygen is limited, such as during intense exercise. Muscles do not metabolize lactic acid for energy at rest.
B. Glucose is a primary fuel source during moderate to high activity, but at rest, muscles rely more on fat metabolism.
C. Creatine phosphate provides a rapid, short-term energy source during the first few seconds of intense activity, but it is not the main energy source at rest.
D. At rest, skeletal muscles primarily metabolize fatty acids through aerobic respiration to produce ATP. This is because fat provides a more efficient and long-lasting energy source during periods of low demand.