Large quantities of information, as well as some timely help ________ since the organization was built.

A．has offered

B．had been offered

C．have been offered

D．is offered

下列各微粒属于等电子体的是

A．N₂O₄和 NO₂

B．CH₄和 NH₄⁺

C．CO₂和NO₂

D．C₂H₆和N₂H₆