Find one mistake in each sentence and correct it

Find one mistake in each sentence and correct it.

1.     Europa might have liquid water and sources of energy that is necessary for life.

     2.  Scientists believe that liquid water might exists below the surface.

     3.  The surface pressure of Titan’s atmosphere is higher than that but the temperature is extreme cold.

     4.  The boy asked if he can fly to the Moon in the future.      

     5.  She suddenly asked me that what I would have done if there had been a war between humans and aliens.