Select the most appropriate synonym of the given word.
Duo

The correct answer is Pair.

Let us break down the meaning of the given word and examine the options to find the most appropriate synonym:

1. Duo: This word refers to a pair of people or things, especially when they are associated or work together (e.g., a comedy duo, a musical duo). Its root comes from the Latin word for "two". Therefore, its core meaning is a set of two, or a pair.
2. Bond: This refers to a connection, link, or union between people or groups, or a legal/financial contract. While a bond can exist between a duo, it is not a direct synonym for the number two or a set of two.
3. Pair: This refers to a set of two things used together or regarded as a unit. This directly matches the definition of "duo".
4. Loan: This refers to a sum of money or an item that is borrowed and expected to be paid back.
5. Debt: This refers to something, typically money, that is owed or due.

By comparing the definitions, we can clearly see that Pair is the closest and most appropriate synonym for Duo.