The pathognomonic sign of measles is Koplik's spot. You may see Koplik's spot by inspecting the:

Correct Answer: B

Rationale: The correct answer is B: Buccal mucosa. Koplik's spots are small white spots surrounded by a red halo that appear on the buccal mucosa opposite the molars. This is a pathognomonic sign of measles due to the presence of the measles virus in the mucous membranes. Inspecting the nasal mucosa (Choice A) would not reveal Koplik's spots. Similarly, examining the skin on the abdomen (Choice C) or the skin on the antecubital surface (Choice D) would not show Koplik's spots as they are specific to the buccal mucosa.

Correct Answer: D

Rationale: The correct answer is D because using mosquito-repelling soaps is not an effective method for malaria control. Malaria is primarily spread through the bites of infected mosquitoes, so focusing on preventing mosquito breeding and bites is key. Let's break it down: A - Chemically treated nets prevent mosquito bites, reducing malaria transmission. B - Introducing larva-eating fish can reduce mosquito populations by eating mosquito larvae. C - Destroying breeding sites eliminates mosquito breeding grounds, reducing the mosquito population and the risk of malaria transmission. D - Mosquito-repelling soaps may help to repel mosquitoes temporarily but do not address the root cause of malaria transmission.

Correct Answer: B

Rationale: Step-by-step rationale: 1. S. japonicum is endemic in the Philippines based on historical data and prevalence studies. 2. S. mansoni is not endemic in the Philippines; it is commonly found in Africa and South America. 3. S. malayensis is a fictional species and does not exist in reality. 4. S. haematobium is primarily found in Africa and the Middle East, not in the Philippines. Summary: The correct answer is B (S. japonicum) because it is the species known to be endemic in certain regions of the Philippines. Choices A, C, and D are incorrect because S. mansoni is not endemic, S. malayensis is fictional, and S. haematobium is not found in the Philippines.

Correct Answer: B

Rationale: The correct answer is B: Using a condom during each sexual contact. This is the best control measure for AIDS because condoms are highly effective in preventing the transmission of HIV, the virus that causes AIDS. Condoms create a barrier that reduces the risk of HIV transmission through sexual contact. Being faithful to a single partner (A) may reduce the risk but does not eliminate it entirely. Avoiding sexual contact with commercial sex workers (C) is not a practical solution for everyone and does not address the risk of transmission in other sexual encounters. Making sure that one's partner does not have signs of AIDS (D) is unreliable as many individuals may be asymptomatic carriers of the virus.

Correct Answer: A

Rationale: The correct answer is A: Contact tracing. Contact tracing involves identifying and notifying individuals who may have been exposed to a sexually transmitted infection (STI) by an infected person. This method helps to break the chain of transmission and prevent further spread of the infection. It is considered the best method for determining possible sources of STIs as it directly targets individuals who have had close contact with an infected person. Summary: B: Community survey - While community surveys can provide valuable data on STI prevalence, they may not accurately identify specific sources of infection. C: Mass screening tests - Mass screening tests can detect STIs in a population, but they do not pinpoint the exact sources of the infections. D: Interview suspects - Interviewing suspects may be useful in some cases, but it may not reach all individuals who have been exposed to an STI. Contact tracing is a more comprehensive approach.