The velocity of exit waste gases should be a minimum of ________of wind speed to prevent down draught.

The velocity of exit waste gases should be a minimum of ________of win

1.	The velocity of exit waste gases should be a minimum of ________of wind speed to prevent down draught.
A.	\(\frac{1}{2}\)
B.	\(1\frac{1}{2}\)
C.	\(2\frac{1}{2}\)
D.	\(3\frac{1}{2}\)
Answer» D. \(3\frac{1}{2}\)