Quiz

1. Where can you find the proto files for the well-known types?
   1. Nowhere; this is hidden inside the Protobuf language.
   2. Nowhere; we need to define them ourselves.
   3. On the GitHub repository under the src/google/protobuf folder.
2. Where can you find the message definitions for the option types?
   1. On the GitHub repository under the folder src/google/protobuf in the file called descriptor.proto.
   2. Nowhere; this is hidden inside the Protobuf language.
   3. Nowhere; we need to define them ourselves.
3. Why do we define an UNSPECIFIED value in enums for proto3?
   1. In proto3, enums are closed, so we do not need to.
   2. In proto3, enums are open, and UNSPECIFIED is used as the default value.
   3. It is not needed in proto3, only in proto2.
4. When do we need nesting types inside a message?
   1. When we want to specialize a type with fully qualified names.
   2. When a type is only relevant in the parent context.
   3. All the above.