Which of these is the commonest Computer Operating System?

Correct Answer: C

Rationale: The commonest computer operating system is determined by widespread use across personal computers globally. 'Windows,' is correct because it dominates the desktop and laptop market, with over 70% share as of 2025 (per StatCounter data), due to its user-friendly interface and compatibility with most software. 'Linux,' is popular among developers and servers but has a niche desktop audience (under 5%). 'Android,' leads in mobile devices, not traditional computers, despite its Linux base. 'MS-DOS,' is outdated, used in the 1980s-90s, not today. Windows' prevalence in homes, offices, and education, driven by Microsoft's marketing and legacy, outstrips competitors in general computer use (excluding mobile-specific OS), making C the clear answer, supported by current industry statistics.

Correct Answer: D

Rationale: Ease, convenience, and cost favor a drug route requiring minimal equipment or expertise. 'Oral,' is correct because it involves swallowing a pill, needing no needles or medical staff, as per pharmacoeconomics (e.g., DiPiro's Pharmacotherapy). 'Intramuscular,' requires injections, less convenient. 'Intravenous,' needs IV setup, costly and complex. 'Subcutaneous,' also involves needles, less simple. Oral administration's widespread use—cheap, self-administered, and non-invasive—makes D the standout answer, reflecting its practicality in outpatient care.

Correct Answer: A

Rationale: Fires fueled by combustibles like paper are Class A fires, best extinguished by cooling and soaking. 'Pressurized water,' is correct because it douses flames and prevents reignition, per fire safety standards (e.g., NFPA). 'Compressed gas,' (e.g., CO2) suits electrical fires (Class E), not paper. 'Liquid soap,' is ineffective and impractical. 'Graphite powder,' is not a standard extinguisher. Water's efficacy on Class A materials—wood, paper—makes A the precise answer, aligned with firefighting protocols.

Correct Answer: D

Rationale: A good research topic should be clear, measurable, and relational. 'Must have at least one variable,' is correct as the exception because a topic may broadly identify an area without specifying variables initially (e.g., Nurse burnout'), per research design (e.g., Leedy & Ormrod). 'Must state relationship between variables,' ensures focus. 'Must be clear and unambiguous,' aids understanding. 'Variables must be measurable,' ensures testability. Topics can start general, refining variables later, making D the least essential trait.

Correct Answer: B

Rationale: Tactile cells (Merkel cells) in the skin detect touch and pressure. 'Tactile cells,' is correct, linked to sensory nerve endings, per histology (e.g., Ross & Pawlina). 'Dendritic cells,' are immune-related. 'Keratinocytes,' form the skin barrier, not sensory. 'Melanocytes,' produce pigment. Tactile cells' mechanoreceptor role makes B the accurate answer.