孔板阀又叫孔板切换阀，是一种类似阀门的流量节流装置，它的作用在于不需要停气或倒换气体流程就可以在()完成更换孔板操作。

(A)2min内;

(B)数分钟内;

(C)10min;

(D)30min

I’ve already told you that I’m going to buy a new iPad, _____.

A．how much does it cost

B．however much it costs

C．no matter how it costs

D．however does it cost much