---Would you like to go and see Avatar with me tonight?

--- Thank you very much , but I     it already.

A．see

B．will see

C．have seen

D． am seeing

有一根50m长的冷拨钢丝，冷拉率控制在4.5%，为达到控制冷拉率，冷拉时最终的长度应该是______m。