Which of the following data types allows for both letters and numbers?

The correct answer is the data type that allows for both letters and numbers, which is a string. A string is a sequence of characters, and it can include letters, numbers, symbols, and even white spaces. This versatility makes strings essential for handling textual data in programming.

On the other hand, characters, integers, and floating-point numbers each serve more specialized purposes. A character data type typically represents a single letter or symbol. An integer data type is exclusively used for whole numbers without decimals, while a float is used for representing decimal numbers. These types are not designed to accommodate a combination of letters and numbers, making string the ideal choice for scenarios that require the storage of mixed alphanumeric data.