Final answer:
The rule of nines is the most helpful guideline for estimating the percentage of total body surface area involved in a burn, being particularly useful for adult patients.
Step-by-step explanation:
The most helpful guideline when estimating the percentage of total body surface area involved in a burn on a 17-year-old male patient is C) The rule of nines. The rule of nines is used to divide the body into areas that represent 9% or multiples of 9% of the total body surface area. It is especially useful for adult patients to quickly estimate the extent of burn coverage and is crucial for making decisions about the need for specialized treatment and fluid resuscitation.