Final answer:
Microorganisms need macronutrients such as carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur in large quantities for cellular structure and metabolism, making macronutrients the correct answer.
Step-by-step explanation:
Microorganisms, like all cells, require certain substances called nutrients to build all of the molecules essential for their structure and metabolism. These nutrients are classified into two main categories: macronutrients and micronutrients or trace elements. Macronutrients are those that are required by cells in large quantities and include elements such as carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), and sulfur (S) - collectively remembered by the acronym CHONPS.
These macronutrients are integral to cellular processes such as the construction of macromolecules from monomers, and the various metabolic pathways that cells use to obtain energy. Macronutrients also include other elements such as potassium (K), magnesium (Mg), calcium (Ca), and sodium (Na), necessary for prokaryotic growth and enzyme function. Therefore, the correct answer to the question is 'C. macronutrients', as these are required in the largest amounts for use in cell structure and metabolism by microorganisms.