a

reference is a variable which hold address that indicates where an object is stored.

a

reference is a special type for declare classes in Ruby.

a

reference is an instance of a class.

a

reference is a variable which point to initialize method defined in a class.

all

of the above is true.

an

object can be thought of as a factory that makes classes.

an

object is a special type for grouping similar variables.

an

object is an instance of a class.