Which is a characteristic of a strong base?
it turns pink phenolphthalein colorless.
it turns blue litmus paper red.
it releases h+ ions into a solution.
it removes h+ ions from solution.

Answer is: It removes H+ ions from solution.

For example sodium hydroxide is strong base.

Chemical dissociation of sodium hydroxide in water:  

NaOH(aq) → Na⁺(aq) + OH⁻(aq).

Strong bases turn colorless phenolphthalein pink, turn red litmus paper blue and release OH⁻ ions into a solution.

Strong base removes H+ ions from solution:

NaOH(aq) + HCl(aq) → NaCl(aq) + H₂O(l).

Net ionic reaction: OH⁻(aq) + H⁺(aq) → H₂O(l).