Which of the following is a complex type in Avro?

• A. Enum
• B. Long
• C. String
• D. Null

Answer: (A)

In Avro, types are split into primitive scalars and complex, named structures. An enum is a complex type because it defines a named type with a fixed set of allowed symbols, representing a restricted domain rather than a single primitive value. This makes it a composite data type you can use inside records or unions to model finite options, like suits or status codes.

The other options are primitive types: long is a 64-bit integer, string is a sequence of characters, and null represents the absence of a value. They are simple scalar values and do not define a structured set of permitted values.