The standard penetration test is performed in clear hole of _____________ mm in diameter.

The standard penetration test is performed in clear hole of __________

1.	The standard penetration test is performed in clear hole of _____________ mm in diameter.
A.	10 to 30
B.	30 to 50
C.	55 to 150
D.	150 to 1000
Answer» D. 150 to 1000