Give an example of
(a) a physical quantity which has a unit but no dimensions
(b) a physical quantity which has neither unit nor dimensions
(c) a constant which has a unit
(d) a constant which has no unit.

Explanation

Plane angle `theta=(l)/(r)` radian
its unit is radian but `[theta]=M^(0)L^(0)T^(0)`
(b) Strain `=(Deltal)/(l)=("Change in length")/("origianl length")`
It has neither unit nor dimensions
(c) Gravitational constant.
`[G]=6.67xx10^(-11)(N*m^(2))/(kg^(2))`
(d) Reynold.s number is a constant which has no unit.