某无色透明溶液，能与铝反应放出H₂，此溶液中可以大量共存的离子组是（   ）

A．H⁺、Mg²⁺、NO₃^-、Ba²⁺

B．K⁺、SO₄^2-、HCO₃^-、Na⁺

C．Ba²⁺、NO₃^-、C1^-、OH^-

D．Cu²⁺、SO₄^2-、C1^-、Na⁺

-I have tried very hard to work out the problem, but failed.

- Why not turn to our monitor for help? You see, _______.

A．it never rains but pours

B．it's better to think twice before doing something

C．two heads are better than one

D．a bird in the hand is worth two in the bush