What will be the product obtained when formaldehyde is treated with conc. $NaOD$ followed by treatment with conc. $H_2SO_4$?

Product $(B)$ is :

What product is obtained from the reaction of a Grignard reagent with a ketone?

Consider the reaction sequence and identify $'C'$.
$A + B \xrightarrow{dil \ NaOH / \Delta} C$
(The reaction sequence is: $3,3-\text{dimethylbut-1-ene} \xrightarrow[(ii) Zn/H_2O]{(i) O_3} A + B$)

Which of the following sets of reagents,used in the order shown,would successfully accomplish the conversion shown?

Following compounds are given:
$(i) CH_3-CH_2-OH$
$(ii) CH_3-CO-CH_3$
$(iii) CH_3-CH(OH)-CH_3$
$(iv) CH_3-OH$
Which of the above compound$(s)$,on being warmed with iodine solution and $NaOH$,will give iodoform?