—Can sixteen-year-olds drive their cars to school?

—No. They shouldn't _____ to drive because they are not serious enough. [ ]

A. allow

B. allowed

C. be allowed

D. have allowed

具有下列电子排布式的原子中，半径最大的是(　　)

A.1s²2s²2p⁶3s²3p²                                 B．1s²2s²2p³

C.1s²2s²2p²                            D．1s²2s²2p⁶3s²3p⁴