A student burns a magnesium ribbon in air and dissolves the ash of the ribbon. On pouring one drop each of this solution, first in blue litmus and then in red litmus solution, he would observe that
1. blue litmus turns colourless, whereas the red litmus remains red
2. blue litmus remains blue, whereas the red litmus turns blue
3. blue litmus turns red, whereas the red litmus litmus remains red
4. blue litmus turns red, whereas the red litmus turns blue