A repressor is a transcription factor that negatively regulates expression of a target gene. An activator is a transcription factor that enhances expression of a target gene. Activators and repressors often bind to the same genomic sequence to precisely regulate transcription.

An inhibitor is a factor that modulates a biological or chemical process, such as a cell signaling pathway or an enzymatic reaction, but does not generally bind directly to DNA. An insulator is a protein that forms boundaries between active and inactive genomic regions, but generally does not have a direct effect on a target gene.

The correct answer is operon. Found in prokaryotes and a few eukaryotes, operons allow transcription and translation of all the genes downstream of a promoter simultaneously. This is advantageous because these organisms are able to express a subset of related genes rapidly in response to external or internal stimuli. 

This is simply a matter of vocabulary. Introns do not contain coding sequences, while exons do. "Intron" comes from the word "intragenic," meaning between genes, and therefore between exons. During post-transcriptional modification, introns are spliced out of the initial RNA transcript.

The ribosome is where translation happens, but it requires both mRNA and tRNA. mRNA provides the "recipe" for the order of the amino acids in its codons, each of which corresponds to a specific amino acid in the chain, and the tRNA molecules come in and bind appropriately when their anti-codons are complementary to the mRNA codons. tRNA molecules carry the amino acids to the ribosome, where the actual protein chain is then synthesized.

Transcription factors are proteins that bind to the regulator region of genes in eukaryotes and regulate whether a gene is expressed or not. A TATA-box binding protein is recruited after the transcription factors bind to the regulator region, and it eventually recruits RNA polymease. Tyrosine recombinases are not involved in initating eukaryotic gene expression.

The soma is the cell body of the neuron (D). The soma is the site of neuron metabolism and protein synthesis.

The dendrites of the neuron (A) receive incoming action potential signals. The axon (B) sends the action potential outward from the soma to the axon terminal (C). Vesicles of neurotransmitter are released from the axon terminal to the dendrites of other nearby neurons. Neurons can have numerous dendrites, but will only have one soma and one axon.

The cerebellum is responsible for maintaining balance and coordination.

The medulla oblongata is responsible for maintaining subconscious body functions, such as heart rate and breathing. The cerebrum is responsible for higher level functions such as movement and memory. The thalamus mediates survival instincts, including hunger, thirst, and sexual instinct.

The central nervous system is composed of the brain (including the cerebrum and brain stem) and spinal cord. Cranial and spinal nerves branch directly off of these structures, but are considered part of the peripheral nervous system.

The nervous system is used to conduct electrical signals throughout the body. These signals stimulate various functions, frequently causing muscles to contract or carrying sensory signals to the brain. The brain and spinal cord are key components for organizing and interpreting these signals.

Neurons are the cells responsible for conducting electrical impulses. The impulses themselves are known as action potentials.

Glial cells provide support for the nervous system. Different types of glial cells perform different functions, such as myelination of axons, immune activity, and the production of cerebrospinal fluid. The cerebellum is a region of the brain responsible for balance and coordination. Since the cerebellum is a part of the nervous system, its structure is primarily composed of neurons. Mitochondria are organelles found in most eukaryotic cells. They generate ATP, which provides energy to the cell. Their function is not inherently linked to the nervous system.

Glial cells provide support for neurons. Schwann cells, oligodendrocytes, astrocytes, and ependymal cells are a few examples of glia. Schwann cells and oligodendrocytes provide myelination for neurons. Astrocytes play a key role in supporting the blood-brain barrier, while epedymal cells are responsible for secreting and circulating cerebrospinal fluid.

Blood vessels provide oxygenated blood and nutrients necessary for proper neuronal function. Connective tissue is a large component of the dura surrounding the brain itself, but it doesn't provide support for neurons themselves. Similarly, epithelial cells help structurally support the blood-brain barrier, but do not interact directly with neurons. Mitochondria are not a cell type, but are an organelle found within neurons.