Environment-friendly Olympics requires Beijing to improve its environment,       turning it into an ecology-friendly city.

A．eventually

B．specially

C．absolutely

D．traditionally

下列各组物质中，化学键的类型相同的是

A．CaCl₂和Na₂S

B．Na₂O和Na₂O₂

C．N₂和Ne

D．HCl和NaOH