已知等差数列{a_n}中，a₇+a₉=16，a₄=1，则a₁₂的值是[ ]

A．15

B．30

C．31

D．64

汉译英：“承兑交单；付款交单；货到即付”，正确的翻译为( )。

A．document against acceptance；document against payment；payment against arrival

B．document against payment；document against acceptance；payment against arrival

C．document against acceptance；payment against arrival；document against payment

D．payment against arrival；document against payment；document against acceptance