Which of the following is high speed steel?

• A. T 55 Ni Cr 65 Mo 30
• B. T 75 W 18 Co 6 Cr 4
• C. T 10 Cr 5 Mo 75 V 23
• D. T 75 W 18 Co 6 Cr 4 V 1 Mo 75
• E. None of the above