To determine the Froude number at the beginning of a hydraulic jump in a rectangular channel, we need to use the sequent depth ratio. The sequent depth ratio (Y2/Y1) is the ratio of the depth of water after the jump (Y2) to the depth of water before the jump (Y1).

Given that the sequent depth ratio is 16.48, we can use the following equation to find the Froude number at the beginning of the jump:

F1 = √(2gY1) / (V1)

Where:
F1 = Froude number at the beginning of the jump
g = acceleration due to gravity
Y1 = depth of water before the jump
V1 = velocity of water before the jump

Now, let's solve the equation step by step.

1. Determine the depth of water before the jump (Y1):
Since the sequent depth ratio (Y2/Y1) is 16.48, we can assume that the depth after the jump (Y2) is significantly greater than the depth before the jump (Y1). As a result, we can approximate Y2 as infinity. Therefore, Y1 is equal to Y2 divided by the sequent depth ratio:

Y1 = Y2 / (Y2/Y1) = Y2 / 16.48

2. Substitute the value of Y1 into the equation:
F1 = √(2gY1) / (V1)

3. Simplify the equation:
Since Y2 is very large compared to Y1, we can approximate (√(2gY1) / (V1)) as (√(2gY2) / (V1)). Therefore, the equation becomes:

F1 = √(2gY2) / (V1)

4. Determine the Froude number at the beginning of the jump (F1):
From the given options, we need to find the Froude number that is closest to the calculated value of F1. Without the specific values of g, Y2, and V1, we cannot calculate the exact Froude number. However, based on the given options, the closest value to the calculated F1 is option B, which is 12.0.

Therefore, the correct answer is option B) 12.0.