Correct Answer: A

Rationale: Step 1: Definition - A codon is a sequence of three nucleotides that code for a specific amino acid or signal the start/stop of protein synthesis. Step 2: Function - Codons are essential for translating genetic information into proteins. Step 3: Specificity - Codons are specific in their role of encoding amino acids. Step 4: Examples - Examples like AUG for methionine and UAA, UAG, UGA for stop codons illustrate codon functionality. Step 5: Summary - The correct answer is A (Codon) because it accurately describes the function and specificity of a three-nucleotide sequence in genetic coding. Choices B, C, and D are incorrect as they do not align with the definition and function of a codon.

Correct Answer: B

Rationale: The correct answer is B: Orthomyxovirus type 1. Family Reoviridae includes Orthoreovirus types 1, 2, and 3. Orthomyxovirus belongs to a different family, Orthomyxoviridae. Therefore, B is the correct answer. Orthoreovirus types 1, 2, and 3 are part of the Reoviridae family. Choice A, C, and D are incorrect because they are all part of the Reoviridae family which includes Orthoreoviruses.

Correct Answer: B

Rationale: The correct answer is B: Macrolides. Listeriosis is typically treated with antibiotics such as Penicillin and ampicillin due to their effectiveness against Listeria monocytogenes. Macrolides, on the other hand, are not first-line agents for listeriosis treatment. They are less effective in treating this bacterial infection compared to Penicillin and ampicillin. Cephalosporins may also be less effective against Listeria monocytogenes compared to Penicillin and ampicillin. Choice D is incorrect as Macrolides are not suitable for listeriosis treatment.

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pneumoniae. This bacterium is the most common cause of bacterial pneumonia in adults. It is a leading cause of community-acquired pneumonia. Streptococcus pneumoniae is known for its ability to infect the respiratory tract and cause inflammation in the lungs leading to pneumonia. Mycobacterium tuberculosis causes tuberculosis, not pneumonia. Escherichia coli is associated with urinary tract infections and gastrointestinal illnesses, not pneumonia. Clostridium botulinum causes botulism, a severe form of food poisoning, but not pneumonia. Therefore, the correct choice is Streptococcus pneumoniae as it is specifically known for causing pneumonia.

Correct Answer: A

Rationale: Rationale: The symptoms described are consistent with Balantidiasis, caused by the parasite Balantidium coli. The presence of ciliated oval organisms in the feces is characteristic of this disease. Ulcers in the large intestine are common in Balantidiasis due to tissue invasion by the parasite. Headache, fever, and abdominal pain are typical symptoms. Other choices can be ruled out: B) Amebiasis presents with similar symptoms but usually involves the liver. C) Toxoplasmosis typically presents with lymphadenopathy and flu-like symptoms. D) Lambliasis usually causes watery diarrhea without blood or mucus. Therefore, the correct answer is A: Balantidiasis.