What may be affected if the diet lacks enough protein?

Correct answer: Tissue repair

Protein supplies amino acids required for growth, maintenance, enzyme formation, immune substances, and repair of damaged tissues. When protein intake is inadequate, wound healing may become slower and the body may have difficulty replacing or rebuilding cells. Temperature regulation is controlled mainly by the nervous and endocrine systems, although nutrition supports normal metabolism. Tooth enamel formation depends especially on proper mineralisation, including calcium and phosphate, rather than being the primary function tested here. Thus, tissue repair is the best answer.