You are given a fairly old piece of dicot stem and a dicot root. Which of the following anatomical structures will you use to distinguish between the two?

$A$ vertical $U-$tube of uniform inner cross-section contains mercury in both sides of its arms. $A$ glycerin (density $= 1.3 \ g/cm^3$) column of length $10 \ cm$ is introduced into one of its arms. Oil of density $0.8 \ g/cm^3$ is poured into the other arm until the upper surfaces of the oil and glycerin are in the same horizontal level. Find the length of the oil column. (Density of mercury $= 13.6 \ g/cm^3$) (in $cm$)

If the altitudes of a triangle are in arithmetic progression,then the sides of the triangle are in

$A$ plano-convex lens fits exactly into a plano-concave lens. Their plane surfaces are parallel to each other. If the lenses are made of different materials of refractive indices $\mu_1$ and $\mu_2$ and $R$ is the radius of curvature of the curved surface of the lenses,then the focal length of the combination is

$A$ solid has a structure in which $W$ atoms are located at the corners of a cubic lattice,$O$ atoms at the centre of edges,and $Na$ atoms at the centre of the cube. The formula for the compound is

Which pyrimidine bases are present in $DNA$?