Which of the following is responsible for causing gonorrhea?

Correct Answer: A

Rationale: Neisseria gonorrhoeae is the correct answer because it is the specific bacterium responsible for causing gonorrhea. It is a sexually transmitted infection that primarily affects the genital tract. Neisseria gonorrhoeae is transmitted through sexual contact and can lead to symptoms such as painful urination, discharge, and pelvic pain. Chlamydia trachomatis (Choice B) is another sexually transmitted bacterium, but it causes chlamydia, not gonorrhea. Mycobacterium tuberculosis (Choice C) is responsible for tuberculosis, a different infectious disease that primarily affects the lungs. Treponema pallidum (Choice D) causes syphilis, another sexually transmitted infection that presents with distinct symptoms from gonorrhea. Therefore, Neisseria gonorrhoeae is the correct choice for causing gonorrhea due to its specific association with this particular infection.

Correct Answer: A

Rationale: Step 1: Streptococcus mutans is known for its ability to produce acids that contribute to the demineralization of tooth enamel, leading to dental caries. Step 2: Streptococcus pneumoniae is a common cause of respiratory infections, not dental caries. Step 3: Bacillus anthracis causes anthrax, a serious bacterial infection, not dental caries. Step 4: Clostridium botulinum causes botulism, a severe form of food poisoning, not dental caries. Summary: Streptococcus mutans is the correct answer as it is specifically associated with causing dental caries, while the other choices are linked to different diseases.

Correct Answer: C

Rationale: The correct descending order of taxonomic categories is domain, kingdom, phylum, class, order, family, genus, species. This hierarchical classification system helps organize and categorize living organisms based on their shared characteristics and evolutionary relationships. Explanation: - Domain is the broadest category, representing the highest level of classification. - Kingdom further divides organisms into major groups based on similar characteristics. - Phylum, class, order, family, and genus successively narrow down the classification based on more specific shared characteristics. - Species is the most specific category, representing individual organisms capable of interbreeding. Summary of other choices: A: Incorrect as it has the incorrect order of phylum, kingdom, and division. B: Incorrect as it has the incorrect order of family and species. D: Incorrect as it has the incorrect order of domain, kingdom, and class.

Correct Answer: B

Rationale: The correct answer is B: Vibrio cholerae. Cholera is caused by Vibrio cholerae, a bacterium that produces a toxin leading to severe diarrhea and dehydration. Clostridium botulinum (A) causes botulism, Salmonella enterica (C) causes salmonellosis, and Escherichia coli (D) can cause various illnesses but not cholera. Vibrio cholerae is the only bacteria specifically known for causing cholera.

Correct Answer: A

Rationale: Step-by-step rationale: 1. IgG is the most abundant immunoglobin in a normal healthy adult due to its long half-life and diverse functions. 2. It plays a crucial role in immune response by neutralizing pathogens and enhancing phagocytosis. 3. IgA is mainly found in mucosal areas, IgE is involved in allergic reactions, and IgD's function is not fully understood. 4. Therefore, IgG is the correct answer as it is the predominant immunoglobin in circulation, providing broad immune protection.