In 2020, this global pandemic led to widespread lockdowns, remote work, and mask mandates.

Making up about 78% of the Earth's atmosphere, this gas is by far the most abundant element in the air we breathe.

This is the most commonly used letter in the English language, appearing in roughly 11% of all words.

This is the only number that cannot be represented by Roman numerals.

This planet has the most moons currently known in our solar system.

In 1989, crowds celebrated as this barrier separating East and West Berlin was opened.

Absorbing most of the sun's harmful radiation, the ozone layer is found nestled within this specific atmospheric layer.

Aside from "I", this is the only other single-letter word that is officially recognized in standard English.

This is the only even prime number.

This chemical element is represented by the symbol W.

This 1986 nuclear disaster in present-day Ukraine remains one of history's worst nuclear accidents.

This is the lowest layer of Earth's atmosphere, where almost all weather occurs and where we live.

This is the only letter in the English language that does not appear in the name of any US state.

If you spell out numbers in order starting from one, this is the very first number to contain the letter "A".

The largest ocean on Earth.

In 2022, this country's full-scale invasion by Russia became Europe's largest armed conflict since World War II.

This instrument revolutionized meteorology by measuring atmospheric pressure.

This is the only letter in the English alphabet that has more than one syllable when spoken aloud.

If you write out the numbers from 1 to 100 in English words, this specific letter is used exactly once (in the number 100).

This African nation is completely surrounded by South Africa.

The 2015 international agreement sought to limit global warming by reducing greenhouse gas emissions.

Accounting for about 0.93% of the air, this element is the third most common gas in Earth's atmosphere.

Counting down from the beginning of the alphabet, this is the last vowel to appear in alphabetical order.

DAILY DOUBLE: This number is the lowest number that is exactly divisible by all single-digit numbers from 1 through 10.

In chess, this is the only piece that can jump over other pieces.