[Solved] Codes located in slanted brackets [ ] indicate that the code _______. A) must be assigned as a secondary code B) must be assigned as principal C) is optional D) was replaced with the code not in brackets Microbiology: The branch of science concerned with microorganisms and their effects on other living organisms. Surface Anatomy: The study of the external features of the body and their relationship to deeper structures, as visible to the naked eye without dissection. Organelle: Specialized structures within a cell, each performing specific functions necessary for the cell's life, such as mitochondria, the Golgi apparatus, and the nucleus. Tissue Types: Categories of tissues in the body, including epithelial, connective, muscle, and nervous tissues, each serving specific functions.