下列物质的分子中，既有σ键又有π 键的是(    )

A．C₂H₆

B．HClO

C．CH₄

D．CO₂

_________ money has been spent in building the modern library, where we can read books in our spare time.

A．A large amount of

B．The number of

C．A large number of

D．A great deal