Which of the following is the leap year?

A calendar year is a leap year if it is divisible by 4. However, this ordinary rule is overridden for a century year (a multiple of 100) — a century year is a leap year only if it is also divisible by 400.

Check each century year given in the options against this rule:

• 2100 ÷ 400 = 5.25 → not a whole number, so 2100 is NOT a leap year.

• 1900 ÷ 400 = 4.75 → not a whole number, so 1900 is NOT a leap year.

• 1800 ÷ 400 = 4.5 → not a whole number, so 1800 is NOT a leap year.

• 2000 ÷ 400 = 5 exactly → a whole number, so 2000 IS a leap year.

Among the four options, only 2000 satisfies both conditions for a century leap year (divisible by 4 and by 400); the other three are divisible by 100 but fail the divisibility-by-400 test, confirming 2000 is the correct leap year among those given.