Which of the following is a fossil Pteridophyte?

In a compound microscope,the focal lengths of two lenses are $1.5 \ cm$ and $6.25 \ cm$. An object is placed at $2 \ cm$ from the objective lens and the final image is formed at $25 \ cm$ from the eye lens. The distance between the two lenses is $.... \ cm$.

In the given reaction,$A$ is:
$A$ $\xrightarrow{\text{Reduction}} B$ $\xrightarrow{HNO_2} C_2H_5OH$

Bayer's process is used for the purification of Bauxite containing which of the following as a major impurity?

Which of the following compounds is formed by the addition of a mineral acid to an aqueous solution of borax?