I must admit you _____________ but I'm afraid the answer is still no．

A．will try

B．try

C．have tried

D．had tried

放牙钳时下列哪钟方法是错误的

A．钳缘应钳缘长轴应与牙体长轴平行

B．钳缘应钳于病牙牙颈和牙根交界的牙根部

C．钳缘应紧紧夹住病牙的牙冠部以免作脱位运动时滑脱

D．肯定钳缘未侵犯邻牙及牙周软组织