Drive down Main Street; If (street is blocked) { Turn right on 15th Street; Turn left on Pine Street; Turn right on 16th Street; } Else Turn right on 16th Street; This rule about sets of instructions holds true for all of the control structures m entioned in this book, and the rule itself can be described in pseudo-code. If (there is only one instruction in a set of instructions) The use of curly braces to group the instructions is optional; Else { The use of curly braces is necessary; Since there must be a logical way to group these instructions;