Which of the following is an uncountable noun?

The correct answer is Money. An uncountable noun (also called a mass noun) is a word that cannot be counted with numbers and does not typically have a plural form. Among the options:

• Coin: Countable (you can have one coin, two coins).
• Note: Countable (one note, two notes).
• Money: Uncountable; you cannot say "one money" or "two moneys"; it is a mass noun referring to currency in general.
• Dollar: Countable (one dollar, two dollars).

Therefore, the uncountable noun is "Money".