How to groupBy using multiple columns in Scala collections?

Choose correct output using the code?

Statement that is not correct for Scala's mutable.Map?

The map method on List (and Seq), transforms each element of a collection based on a function. For example, if we have a List[String] and want to convert it to all lowercase?

What is the output?

Which one is not valid using List?

For the type heirachy defined below, Choose the most correct statement below for the output?

Given the type hierarchy defined below, Choose correct statement below?

Choose the expression that allows the code to compile

For given code, Choose correct statement which explains the error?

Choose description that describes the Scala classes 'scala.AnyRef ' and 'scala.AnyVal'?