$\mathrm{Ethyne} \stackrel{?}{\to }$ $\mathrm{Benzene}$ 

The reagent used in the above conversion is:

1. Cr₂O₃

2. Alc. KOH

3. Red hot Fe

4. NaNH₂/liq.NH₃

RCOCl and ${\mathrm{AlCl}}_3$ are used in the Friedel-Crafts reaction.
The electrophile among the following is:

1. ${\mathrm{Cl}}^{+}$                                       

2. RCOCl

3. $\mathrm{R}\stackrel{+}{\mathrm{C}}$O                                     

4. ${\mathrm{R}}^{+}$

Product (B) in the above mentioned reaction is-

1.		2.
3.		4.