The basic unit of speed is
(A). $ \dfrac{Km}{min}$
(B). $\dfrac{m}{min}$
(C). $\dfrac{km}{h}$
(D). $\dfrac{m}{s}$

Hint: Here with the help of definition of speed write the formula of speed.

Complete step-by-step solution -
The speed of an object in an interval of time is the distance traveled by the object divided by the duration of the interval.
Since, \[speed = \dfrac{{\text{distance travelled}}}{{\text{time taken}}}\]
Unit of \[speed = \dfrac{{{\text{unit distance}}}} {{{\text{unit time}}}}\]
Because unit of distance = m, and unit of time = s
Unit of speed $ = \dfrac{m}{s}$
Hence option D is correct answer.

NOTE: First we have to know the definition of speed and then by definition write the formula of speed and put the units that are used in the formula to find the unit.