The accessory glands of the human male reproductive system are:

$A$ parallel plate capacitor with air between the plates has a capacitance of $9 \, pF$. The separation between its plates is $d$. The space between the plates is now filled with two dielectrics. One of the dielectrics has dielectric constant $K_1 = 3$ and thickness $d/3$,while the other one has dielectric constant $K_2 = 6$ and thickness $2d/3$. The new capacitance of the capacitor is ........ $pF$.

Which of the following pairs represents linkage isomerism?

Assertion $(A)$: White tin is an example of a tetragonal system.
Reasoning $(R)$: For a tetragonal system,$a=b=c$ and $\alpha=\beta=\gamma \neq 90^{\circ}$. The correct answer is

Oxalic acid reacts with concentrated $H_2SO_4$ to give a mixture of two gases. When this mixture is passed through caustic potash,one of the gases is absorbed. What is the product formed by the absorbed gas with caustic potash?

Which of the following is an industrial fuel?