Most enzymes are

A. DNA is a long, double-stranded molecule made up of A, T, G, and C bases: DNA consists of two complementary strands forming a double helix. Its sequence of adenine (A), thymine (T), guanine (G), and cytosine (C) encodes genetic information for protein synthesis and inheritance.

B. tDNA is considered a "molecular slave" of DNA during protein synthesis: There is no molecule called tDNA. Transfer RNA (tRNA) carries amino acids during protein synthesis, but the term “tDNA” is incorrect and does not exist in molecular biology.

C. Three forms exist: DNA, RNA, and tDNA: Only DNA and RNA are recognized types of nucleic acids. tDNA is not a valid classification, so this statement is inaccurate.

D. RNA is a long, single-stranded molecule made up of the bases A, T, G, and C: RNA is single-stranded, but it contains uracil (U) instead of thymine (T). Its bases are adenine (A), uracil (U), guanine (G), and cytosine (C).

A. Spinal cord: The spinal cord is housed within the vertebral cavity, which is part of the dorsal cavity. It is protected by the vertebrae and surrounded by cerebrospinal fluid.

B. Thoracic cavity: The thoracic cavity is part of the ventral cavity, not the dorsal cavity. It contains the heart and lungs and is separated from the abdominal cavity by the diaphragm.

C. Vertebral cavity: The vertebral cavity encloses the spinal cord and is a key subdivision of the dorsal cavity, providing protection and structural support.

D. Cranial cavity: The cranial cavity contains the brain and is located within the skull. It is a major component of the dorsal cavity, working with the vertebral cavity to protect the central nervous system.