Why? I have nothing to confess(坦白). _________ you want me to say?

A．What it is that

B．How is it that

C．How it is that

D．What is it that

加热蛇形分支管道上装有截止阀、过滤器、气动切断阀和减压阀，减压阀用来把总管道蒸汽压力降低到使用点的最佳压力值。