The Odd One Out Challenge: 30 Questions

[B] Penguin | Aquatic theme misleads. Dolphin, manatee, and even egg-laying platypus are mammals; penguins are flightless birds. Monotremes (platypus) prove mammals can lay eggs and still lactate.

[A] 33 | Looks prime beside 29, 31, 37, but 33 = 3 × 11. The others are primes—divisible only by 1 and themselves. Composite gatecrasher identified.

[D] Chlorine | All are gases, but only helium, neon, argon are Group 18 noble gases with full valence shells. Chlorine sits in Group 17 (halogens), reactive and bond-hungry.

[C] Geneva | Italian trio versus a confusable look-alike name. Geneva is in Switzerland; Genoa would be Italian. Precision geography beats spelling vibes every time.

[A] PostgreSQL | Tricky: you "write queries," so it feels like coding. But PostgreSQL is a database; SQL is a query language. Rust, Go, Python are general-purpose languages.

[B] Netherlands | Nordic = Denmark, Finland, Iceland, Norway, Sweden (plus autonomous regions). Netherlands belongs to the Low Countries/Benelux—nearby on a map, outside the Nordic definition.

[C] NFC | All feel "interface-y," but Thunderbolt/HDMI/DisplayPort are cabled connectors. NFC is short-range wireless; no pins, just radio handshakes and tap-to-pair charm.

[D] The Importance of Being Earnest | Oscar Wilde's farcical comedy sneaks alongside three Shakespeare heavyweights. Handbags and cucumber sandwiches, not daggers and ghosts, give it away.

[B] Safari | YouTube, Chrome, Gmail live under Google/Alphabet. Safari is Apple's browser—fast, privacy-forward, and tightly integrated with Apple ecosystems.

[A] NaOH | Hydrochloric, sulfuric, nitric donate protons—classic acids. Sodium hydroxide is a base; it gladly accepts those protons. Pair acid with base and you'll get salt plus water.

[C] Guyana | A classic name trap: Ghana, Guinea, Gabon are African countries; Guyana sits on South America's Atlantic shoulder. Spelling twins, continental opposites.

[D] Lichen | Shiitake, morel, porcini are edible fungal fruiting bodies. Lichen is a symbiosis of fungus with algae/cyanobacteria—great pioneer organism, not a culinary cap-and-stem mushroom.

[B] Lake Champlain | Tempting: it was briefly dubbed a "sixth Great Lake" in funding debates. Official five remain Superior, Michigan, Huron, Erie, Ontario.

[A] Rhombus | Equilateral, isosceles, scalene are triangle classifications by sides. A rhombus is a four-sider with equal edges—great for tiling, terrible at being triangular.

[C] 304 | 400/403/404 belong to client-error 4xx class. 304 "Not Modified" lives in 3xx/conditional cache logic—no error, just "use your cached copy."

[D] Mozart | Three stadium legends versus one prodigy composer. Different centuries, same hooks; still, Wolfgang didn't tour with amps or pyrotechnics.

[B] Natural gas | Wind, sun, and flowing water renew naturally. Fossil methane took ages to form; wonderful energy density, dreadful at replenishing on human project timelines.

[A] Sydney | Dhaka (Bangladesh), Muscat (Oman), Seoul (South Korea) are national capitals. Australia's capital isn't Sydney either—it's Canberra. Sydney hogs postcards, not parliament.

[C] VII | Omega, omicron, lambda hail from the Greek alphabet. VII is a Roman numeral masquerading as letters—useful for clocks, unhelpful for sorority sweaters.

[B] Git | MIT, GPLv3, Apache-2.0 are OSI-approved licenses. Git is the distributed version control tool developers use to time-travel through commits—not a license.

[D] Rooibos tea | Matcha and black tea contain caffeine; yerba mate can rival coffee's buzz. Rooibos is naturally caffeine-free—sweet, earthy, bedtime-friendly.

[A] Sartorius | Radius, ulna, scapula are bones (forearm, forearm, shoulder blade). Sartorius is a long thigh muscle famous for crossing your legs like a tailor.

[C] Jamón ibérico | Brie, Camembert, Roquefort are French dairy royalty. Jamón ibérico is Spain's acorn-luxe cured ham—sublime pairing, but not a cheese.

[D] NASDAQ | Litecoin, XRP, Polkadot are blockchain tokens. NASDAQ is a U.S. stock exchange/index—tickers, earnings, and market makers, not wallets and block explorers.

[B] Metaphor | Sonnet, haiku, ballad prescribe structure. Metaphor is a figure of speech—meaning teleporter, not a verse blueprint. Lovely, but formally unmetered.

[A] Belize | South America cluster: Suriname, Guyana, Ecuador. Belize belongs to Central America—Caribbean coasts, barrier reefs, Mayan sites, different continental club.

[C] JSON | PATCH, OPTIONS, HEAD are real HTTP methods. JSON is a data format for payloads. Useful in bodies and responses, not on the request-line verb slot.

[D] Jupiter | Mercury, Venus, Earth are rocky terrestrial worlds. Jupiter is a hydrogen-helium gas giant with no solid surface—stunning bands, lousy hiking.

[B] H2O | A, AB, O are ABO blood groups. H2O is water—essential for life, catastrophically wrong for transfusions. Hydrate before quizzes; don't "donate" it.

[A] QuickSort | Hash maps, trees, stacks store/organize data. QuickSort is an algorithm that partitions and recurses to order lists—great at tidying, terrible at holding anything.