What is the opposite approach to the lexical scoping?

Consider the code snippet given below

var count = [1,,3];

A. The omitted value takes “undefined”

B. This results in an error

C. This results in an exception

D. None of the mentioned

Consider the following code snippet

var a1 = [,,,]; 
var a2 = new Array(3); 
0 in a1 
0 in a2

A. true false

B. false true

C. true true

D. None of the above

The pop() method of the array does which of the following task ?

A. decrements the total length by 1

B. increments the total length by 1

C. prints the first element but no effect on the length

D. None of the mentioned

Consider the following code snippet :

if (!a[i]) continue ;

A. Skips the undefined elements

B. Skips the non existent elements

C. Skips the null elements

D. All of the mentioned