Consider
	sig Object { rel: Object -> Object }
Let a, b:Object. What does the expression a.(b.rel) evaluate to?
	 1 The field a.b.rel. 
	 2 Nothing; it is undefined
	[3] The set of all Objects that b.rel associates with a
	 4 A relation of type Object -> Object -> Object -> Object. 

Message for incorrect answer: Wrong. Take a look at <a href = "http://www.doc.ic.ac.uk/project/2007/271j/g06271j01/Web/tutorial2_2.php#dot_operator">Dynamics II</a> to find the answer.