Which of the following reactions will yield $2,2$-dibromopropane as the product?

To convert $1$-butyne to $1-D$-butanal,one would carry out the following steps :
$(I)$ Sodium amide,then $D_2O$
$(II)$ Disiamylborane,then hydrogen peroxide/sodium hydroxide
$(III)$ The transformation can not be carried out with the indicated reagents.

When acetylene is passed through a solution of dilute sulfuric acid containing mercuric sulfate,the number of $\pi$ bonds in the final product obtained is.........

Which of the following bonds makes a hydrocarbon most reactive?

Identify the major product $A$ in the following reaction sequence:
$CH_3-CH=CH-CH_3$ $\xrightarrow[CCl_4]{Br_2}$ $\xrightarrow[(ii) NaNH_2]{(i) alc. KOH} (A)$

Propene and propyne can be distinguished by