He never ______learning English. That was why he was successful at last.

A．gave in

B．gave out

C．gave up

D．gave away

25℃时，在pH=13的溶液中可以大量共存的离子组是[ ]

A．K⁺、Na⁺、HCO₃^-、NO₃^-

B．Na⁺、K⁺、SO₄^2-、Cl^-

C．H⁺、Mg²⁺、SO₄^2-、NO₃^-

D．Ag⁺、K⁺、NO₃^-、Na⁺