169.  Most economical section of a triangular channel, is
A. equilateral triangle
B. right angled triangle
C. isosceles triangle with 450 vertex angle
D. right angled triangle with equal sides.

---

170. Most economical section of a circular channel for maximum discharge
A. depth of water = 0.95 diameter of circular section
B. hydraulic mean depth = 0.286 diameter of circular section
C. wetted perimeter = 2.6 diameter of circular section
D. all the above.

---

171. Most economical section of a circular channel for maximum velocity, is if,
A. depth of water = 0.810 diameter
B. hydraulic mean depth = 0.304 diameter
C. wetted perimeter = 2.245 diameters
D. all the above.

---

172. The most efficient channel section, is
A. semi-circular
B. rectangular
C. triangular
D. half hexagon in the form of trapezoid.

---

173. Chezy's formula is used to determine
A. head loss due to friction in pipe
B. velocity of flow in pipe
C.- velocity of flow in open channels
D. none of these.

---

174. Pick up the correct statement from the following :
A. For tranquil flow h > NW: or v < ?2
B. For critical flow h = ?v
C. For torrential flow h > ?2 or v <
D. None of these.

---

175.  The phenomenon occuring in an open channel when a rapidly flowing stream abruptly changes to a slowly flowing stream causing a distinct rise of liquid surface, is
A. water hammer
B. hydraulic jump
C. critical discharge
D. none of these.

---