Which of the following is not a Pteridophyte?

How many geometrical isomers are possible for the complex $[Mab(AB)_2]^{\pm n}$?

$A$ block can slide on a smooth inclined plane of inclination $\theta$ kept on the floor of a lift. When the lift is descending with an acceleration $a$,the acceleration of the block relative to the incline is:

Which of the following is a bactericidal antibiotic?

Solid $NaCl$ is a bad conductor of electricity because

Which of the following substances is the least soluble in water?