Pick up the correct statement from the following

Question: Pick up the correct statement from the following

1. the contour lines having the same elevation cannot unite and continue as one line

2. a contour can not end abruptly, but must ultimately close itself not necessarily within the limits of map.

3.the direction of steepest slope at a point on a contour is at right angles to the contour

4. all the above.

Answer:4