$1, 2-$dibromoethane when heated with alcoholic potash gives

$HC \equiv CH$ $\xrightarrow[{excess}]{{CH_3MgBr}} \mathop {(A)}\limits_{\text{salt}} + \mathop {(B)}\limits_{\text{hydrocarbon}}$
$(A)$ $\xrightarrow[{excess}]{{CH_3I}} (C)$ $\xrightarrow[{(ii) H^{+} }]{{(i) NaNH_2}} (D)$

Which of the following is used for the conversion of $2$-hexyne into $trans$-$2$-hexene?

Identify $Z$ in the following series of reaction:
$CH_3-CH_2-OH$ $\xrightarrow[170^{\circ} C]{conc. H_2SO_4} X$ $\xrightarrow[CCl_4]{Br_2} Y$ $\xrightarrow[\Delta]{alc. KOH} Z$

When propyne is treated with dilute $H_2SO_4$ and $HgSO_4$,the major product is

When ethyl bromide reacts with sodium acetylide,the main product is: