When I create a textbox and give it an ID, "myTextbox", the following gets added to the designer.vb file (assuming you are using VB.Net):
Protected WithEvents myTextbox As Global.System.Web.UI.WebControls.TextBox
But that only happens after I give the textbox an ID. I'd say the correct answer is "none of the above". If, however, they must have an answer I'd say the correct one would have to be "b". No event handlers are added unless you double click the textbox, and even then the event handler is for the "text changed" event. So, the event depends on the control created and would not be the click event in all cases. Bring this to your teacher... maybe they will listen.