The correct option is B HO−
Both NH−2 and CH3CH−2 are stronger base than HO− because O is more electroneagtive than N and C, so it will hold the negative charge more strongly. NH−2 and CH3CH−2 will be neutralized quantitatively by water, therefore will not survive in water.
NH−2+H2O→NH3+HO−CH3CH−2+H2O→CH3CH3+HO−
Therefore, the strongest among given base that can survive in water without reacting is HO−