Which compounds among the following give a positive iodoform test?

What is produced when glycerol is heated with oxalic acid at $110\,^{\circ}C$?

Dehydration of an alcohol $(A)$ gives an alkene. Ozonolysis of one molecule of this alkene yields two molecules of acetaldehyde. Identify the alcohol $(A)$.

Which of the following statements is correct regarding the rate of dehydration in alcohols?

In the following sequence of reactions,
$CH_3CH_2CH_2Br$ $\xrightarrow{KOH(alc.)}$ $(A)$ $\xrightarrow{HBr}$ $(B)$ $\xrightarrow{KOH(aq.)}$ $(C)$
The product $(C)$ is

Identify $A, B, C,$ and $D$ in the following reaction sequence:
$CH_3-CH_2-CH(OH)-CH_3$ $\xrightarrow{PBr_3} (A)$ $\xrightarrow{Mg, \text{ether}} (B)$ $\xrightarrow{CH_3CHO} (C)$ $\xrightarrow{H_3O^+} (D)$