A student puts a drop of dilute solution of sodium hydroxide first on a blue paper and then on a red litmus paper. He would observe that
1
the blue paper turns red and the red litmus paper turns blue.
2
There is no change in the blue litmus paper and the red litmus paper turns blue.
3
there is no change in the red litmus paper and the blue litmus paper turns red.
4
the blue litmus paper turns colourless and there is no change in the red litmus paper.