Covariance and Contravariance on the same type argument

Question

The C# spec states that an argument type cannot be both covariant and contravariant at the same time.

This is apparent when creating a covariant or contravariant int

Answer 1

Without out and in keywords argument is Covariance and Contravariance isn't it?

in means that argument can only be used as function argument type

out means that argument can be used only as return value type

without in and out means that it can be used as argument type and as return value type