Extracted text: 1. Critical flow in an open channel occurs, when Froude number is.......(a) less than 1, (b) more than 1, (c) depends on the rainfall, (d) none of these. 2. Manning's formula is used for calculating....(a) aquifer flow, (b) velocity in channel, (c) peak flow, (d) critical depth 3. Hydraulic radius (R) is: a) Ratio between flow area (A) and wetted perimeter (P) b) Ratio between wetted perimeter (P) and flow area (A) 4. Open channel flow is: a) Liquid surface is subject to Hydraulic pressure b) Liquid surface is subject to atmospheric pressure