When $36 \ g$ of a non-volatile,non-electrolytic solute having the empirical formula $CH_2O$ is dissolved in $1.2 \ kg$ of water,the solution freezes at $-0.93 \ ^{\circ}C$. The molecular formula of the solute is ($K_f$ of water $= 1.86 \ K \ kg \ mol^{-1}$)

The synthesis of crotonaldehyde from acetaldehyde is an example of $.......$ reaction.

$A$ parallel beam of light is incident on a system of two convex lenses of focal lengths $f_1 = 20\, cm$ and $f_2 = 10\, cm$. What should be the distance between the two lenses so that the rays after refraction from both the lenses emerge as a parallel beam?........$cm$

$A$ horizontal uniform glass tube of $100 \ cm$ length, sealed at both ends, contains a $10 \ cm$ mercury column in the middle. The initial temperature and pressure of air on either side of the mercury column are $31^{\circ} C$ and $76 \ cm$ of mercury, respectively. If the air column at one end is kept at $0^{\circ} C$ and the other end at $273^{\circ} C$, then the pressure of the air at $0^{\circ} C$ is (in $cm$ of $Hg$):

For a body moving in a circular path,what is the condition for no skidding if $\mu$ is the coefficient of friction?

Identify the blank spaces $a, b, c$ and $d$ given in the following table and select the correct answer.
| Organism | Type | Product |
| :--- | :--- | :--- |
| $a$ | $b$ | Cyclosporin-$A$ |
| $c$ | Bacterium | Butyric acid |
| $d$ | Bacterium | Lactic acid |