Which one of the following pairs of quantities has no length in their dimension?

The dimension of a physical quantity describes the powers of fundamental units (Mass, Length, Time) it contains. A quantity has "no length" if the exponent of Length (L) in its dimensional formula is zero (L⁰).

• Surface Tension: Defined as Force per unit Length (F/l). Its dimensions are [MLT^-2] / [L] = [M¹L⁰T^-2].
• Strain: Defined as the ratio of change in length to original length (ΔL/L). It is dimensionless, represented as [M⁰L⁰T⁰].

Both quantities in Option B have L⁰. In other options, Angular Momentum has [ML²T^-1], Mass Density has [ML^-3], and Pressure Gradient has [ML^-2T^-2], all of which involve length. While Angle is dimensionless ([L⁰]), its pair in option D (Pressure Gradient) contains length.