Intensity of problem is said to be ‘nil / no problem’ if chloride content in irrigation water is

Correct option is B

Chloride content affects irrigation suitability.
Low chloride levels are safe for crops.
Values below 4 meq L⁻¹ cause no toxicity.
Higher levels create salinity problems.
Thus, no problem exists below this limit.
Therefore, < 4 meq L⁻¹ is the correct answer.