下列哪种因素与牙体缺损的成因无关（）

A.楔状缺损

B.重度磨耗

C.牙周病

D.牙外伤

E.龋病

I’ve already told you that I’m going to buy it, ________.

A．how much does it cost

B．no matter how it costs

C．however does it cost much

D．however much it costs