Pick up the correct statement from the following A. Approach of the water line in a flumed channel section should not be steeper than $$22{\frac{1}{2}^ \circ }$$ B. Departure of the water line from a flumed channel section should not be steeper than 30° C. Approach of the water line should not be steeper than 30° and departure line not steeper than $$22{\frac{1}{2}^ \circ }$$ in a flumed channel section D. Approach and departure of the water line in a flumed channel section, should not be steeper than $$22{\frac{1}{2}^ \circ }$$

The correct answer is D.

The approach and departure of the water line in a flumed channel section should not be steeper than $$22{\frac{1}{2}^ \circ }$$. This is to ensure that the water flows smoothly through the channel and does not cause any erosion or damage.

Option A is incorrect because it only specifies the maximum slope for the approach of the water line. Option B is incorrect because it only specifies the maximum slope for the departure of the water line. Option C is incorrect because it specifies different maximum slopes for the approach and departure of the water line, which is not necessary.