Question

Which ion reacts with aqueous sodium hydroxide to give a precipitate that dissolves in an excess of sodium hydroxide?
A Ca2+
B Fe2+
C Fe3+
D Pb2+

Pls explain how to get the ans, thks!
All form a hydroxide insoluble in water. Pb^2+ is the only one to form Pb(OH)2 which dissolves in an excess of NaOH by forming a complex ion of [Pb(OH)4]^2-

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