1 km = ___ m.

**The reasoning** The metric system works in powers of 10, and the prefix "kilo-" always means **1000 times** the base unit. So: - 1 kilometre = 1000 metres - 1 kilogram = 1000 grams - 1 kilolitre = 1000 litres Think of it this way: when you walk from your house to the main road (maybe 500 metres), you've covered half a kilometre. To complete 1 full kilometre, you'd need to walk that distance twice — which equals 1000 metres total. The conversion is straightforward: **1 km = 1000 m** **Why the wrong options tempt you** - **10 (A)** — You might confuse "kilo" with "deca" (which means 10) - **100 (B)** — You might think of "hecto" (which means 100) or mix up different metric conversions - **10000 (D)** — This looks like "kilo" because of all the zeros, but it's actually 10 kilometres, not 1 **Quick takeaway** Remember: **"Kilo" = 1000** — whether it's kilometres, kilograms, or kilowatts, the prefix always multiplies by 1000.