This is because iron is used to make a protein called hemoglobin. This protein helps blood cells carry oxygen around the body.
 
        
             
        
        
        
Answer:
Characteristics such as appearance, reproduction, mobility, and functionality are just a few ways in which living organisms are grouped together. These specialized groups are collectively called the classification of living things.
 
        
             
        
        
        
Answer:
D. The energy is used by organisms for life functions or is lost as heat.
Explanation:
 
        
             
        
        
        
The most appropriate technique that the physician should use to estimate the basal metabolic rate of Louisa's body is indirect calorimetry.
<h3>What is indirect calorimetry?</h3>
Indirect calorimetry is a medical technique for determining a person's resting energy expenditure. This technique is used to calculate the calories your body expends in a resting situation.
Information obtained from indirect calorimetry can be used as a guide to basal metabolism to determine whether it is normal, increased, or decreased. 
Based on the above, this is the best technique the doctor has to find out why Louisa is gaining weight without changing her diet.
Learn more about diet in: brainly.com/question/4539044