What does ? symbol mean if used after object type?

Question

Could someone please tell me what the ? symbol means in the following code:

  public Rectangle? Limits
    {
        get
        {
            return _limits;
        }
        set
        {

Answer 1

It is syntactic sugar for specifying a nullable type.

Answer 2

It means it is a nullable type.

For example, DateTime? can be null, whereas DateTime cannot.