B

Tetracyclines incorporate into developing enamel and dentin; because permanent tooth calcification is largely complete by about 8 years of age, the drug is generally contraindicated in children younger than 8 to avoid permanent yellow-brown discoloration of the teeth [Stultz & Eiland, 2019, PMID 31280586; Sánchez et al., 2004, PMID 15485524].