In a Sarda type fall, the rectangular crest is used for discharge upto 

Concept:

The design features of Sarada Falls are given below;

• Discharge intensity varied from 1.6 to 3.5 m³/s.
• The drop varied from 0.6 to 2.5 m.
• When the discharge of a canal is less than 14 m³/s, the section of the body wall is kept rectangular.
• When the discharge of a canal is more than 14 m3/s, the section of the body wall is kept trapezoidal with upstream batter 1 : 3 and downstream batter 1 : 8.
• The depth of cut-off may range 1 m to 1.5 m

​Hence option (3) is the correct answer.