Gravitational force is required for

Which of the following is a non-living level of biological organization?

The refractive index of a material of a plano-concave lens is $5/3$,and the radius of curvature is $0.3 ~m$. The focal length of the lens in air is (in $~m$)

Which of the following statements is incorrect for physical adsorption?

Write the resonance structures of $CO_3^{2-}$ and $HCO_3^-$.

$A$ body of mass $2 \, kg$ slides down a curved track which is a quadrant of a circle of radius $1 \, m$. All the surfaces are frictionless. If the body starts from rest,its speed at the bottom of the track is ................. $m/s$.