The code mentioned in problem 6 of HW1 is

var x = 5;
function f(y) {return (x+y)-2};
function g(h){var x = 7; return h(x)};
{var x = 10; g(f)};

Assume that this code comes from a bigger code which is :
(function (){
   var x = 5;
      (function (){
            function f(y) {return (x+y)-2};
	          (function (){
		          function g(h){var x = 7; return h(x)};
			          (function (){
				             var x = 10; g(f)};
		                  })()
		  })()
      })()
})()

From this bigger code it is clear that the statements of the original code are contained in 
succesively nested scopes (Each anonymous function call ie (function(){..}) () in the above code, starts a new scope).
This explains why we need a separate activation record for each statement of the original code.