Correct Answer: A

Rationale: Rationale: A: Incorrect - The complement system is not directly involved in the viral neutralization reaction. B: Correct - Specific antibodies neutralize viruses by blocking their ability to infect cells. C: Incorrect - Antibodies are titrated, but only one serum sample is required for neutralization testing. D: Incorrect - Viral neutralization is primarily used to measure antibody response, not to identify newly isolated viruses.

Correct Answer: D

Rationale: The correct answer is D: RTECS number. The Registry of Toxic Effects of Chemical Substances (RTECS) number is a unique identifier assigned to chemicals and substances known to cause toxicological effects. It aids in accessing detailed toxicological information such as acute toxicity, carcinogenicity, and mutagenicity. The CAS number (A) is a unique numerical identifier for chemical compounds, not specifically for toxicological information. The atomic number (B) is the number of protons in an element's nucleus, unrelated to toxicology. The DOT ID number (C) is used for hazardous materials transportation, not for toxicological information. Therefore, the RTECS number is the correct choice for finding toxicological information about a specific substance.

Correct Answer: D

Rationale: The correct answer is D: All of the above. Salmonella enterica, Clostridium botulinum, and Escherichia coli are all commonly associated with food poisoning. Salmonella causes symptoms like diarrhea, vomiting, and abdominal cramps. Clostridium botulinum produces a toxin that leads to symptoms like muscle weakness and paralysis. Escherichia coli can cause symptoms like severe stomach cramps, diarrhea (often bloody), and vomiting. Therefore, all three bacteria are known to cause food poisoning. The other choices are incorrect because each of the bacteria listed is associated with food poisoning.

Correct Answer: C

Rationale: The correct answer is C: Erysipelas. Erysipelas is a type of acute infection caused by group A Streptococcus bacteria. This bacteria infects the upper dermis and superficial lymphatics, leading to a distinct raised, well-demarcated, erythematous skin lesion. The other choices are incorrect because: A Carbuncle is a deep skin infection involving hair follicles, B Impetigo is a superficial skin infection caused by Staphylococcus or Streptococcus bacteria, and D Acne is a chronic inflammatory skin condition not typically caused by group A Streptococcus.

Correct Answer: A

Rationale: Rationale: 1. Gram-positive cocci in pairs indicate Streptococcus pneumoniae. 2. Presence of a capsule points to S. pneumoniae as it has a polysaccharide capsule. 3. S. pneumoniae commonly causes sore throat. 4. Neisseria meningitidis, Haemophilus influenzae, and Klebsiella pneumoniae are not typically associated with sore throat.