Question

1. what is the most effective way to measure body composition? *

body mass index (bmi)
looking in the mirror
skinfold
underwater weighing

Explanation:

Underwater weighing is a highly accurate method for measuring body composition. It uses the principle of density to separate body mass into fat and fat - free components. BMI only considers weight and height, not body composition. Looking in the mirror is subjective. Skinfold measurements have some error due to factors like operator skill.

Answer:

Underwater Weighing