# Which is the most suitable reagent among the following to distinguish compound (3) from rest of the compound(s)?$\begin{array}{1 1}(1)\;CH_3C\equiv C-CH_3&(2)\;CH_3-CH_2-CH_2-CH_3\\(3)\;CH_3-CH_2-C\equiv CH&(4)\;CH_3-CH=CH_2\end{array}$

$\begin{array}{1 1}(a)\;\text{Bromine in carbon tetrachloride}\\(b)\; \text{Bromine in acetic acid}\\(c)\;\text{Alk}.KMnO_4\\(d)\;\text{Ammoniacal silver nitrate}\end{array}$

$Br_2$ in $CCl_4(a),Br_2$ in $CH_3COOH(b)$ and alk.$KMnO_4(c)$ will react with all unsaturated compounds,(i.e) 1,3 and 4 while ammonical $AgNO_3(d)$ reacts only with terminal alkynes (i.e) 3 and hence 3 can be distinguished from 1,2 and 4 by ammoniacal $AgNO_3$
Hence (d) is the correct answer.