Identify the reagent used in the following reaction.
Benzoic acid $\stackrel{\text{Reagent}}{\Delta}$ Benzoyl chloride + Phosphorous oxychloride + Hydrogen chloride

The functional kidney of a frog tadpole is:

Two stars of masses $M$ and $2M$ are at a distance $d$ apart and are revolving around their common center of mass. The angular velocity of the system of two stars is ($G$ is the universal gravitational constant):

The relative reactivities of acyl compounds towards nucleophilic substitution are in the order of

In angiosperms,characters of flowers are used in classification because

Which one of the following frequencies of radiation (in $Hz$) has a wavelength of $600 \ nm$?