undefined. If you do a mathematical operation on an undefined variable your result will be
NaN which means “Not a Number”. If you concatenate a string with an undefined variable, you will get a literal string of “undefined”.
Basically this means that before you do any operations with them you must assign an initial value at some point.
the correct answer is :
// Initialize these three variables
var c=“I am a”;
// Do not change code below this line
a = a + 1;
b = b + 5;
c = c + " String!";