The correct answer is A. cubic metre/sec.
Runoff is the water that flows over the surface of the land after a rainfall or snowmelt event. It is a major component of the water cycle and is an important source of water for many ecosystems.
The unit of runoff in the M.K.S. system is cubic metre/sec. This unit is used to measure the volume of water that flows over a given area in a given amount of time.
The other options are incorrect because they do not measure volume. Option B, metre/sec, is the unit of speed. Option C, cubic metre, is the unit of volume. Option D, square metre, is the unit of area.
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