Answer
Field at point 3 remains same as its distance from center of balloon does not change , field at 1 remains 0 as it remains inside balloon , field at 2 becomes 0 as it come inside the balloon.
Work Step by Step
Balloon can be considered as a hollow charged sphere having charge q on its surface. . Electric field inside a hollow charged sphere is 0 and at a distance x is kq/x.x . x is distance from center of sphere to the point where we need to find the electric field.(x>radius of sphere) The distance b/w center of sphere and point 3 does not change so , electric field remains same for point 3. After expansion the point 2 comes inside the balloon so , its electric field will become 0 and point 1 remain inside balloon so its field remains 0.
