Which of the following aqueous solution will be the best conductor of electricity?

The correct option/answer is HCl.

To determine which aqueous solution will be the best conductor of electricity, we need to understand the behavior of each substance when dissolved in water.
Electrical conductivity in aqueous solutions depends on the concentration of free-moving ions. The greater the concentration of ions, the better the solution conducts electricity.

Let's analyze each of the given options:

1. HCl (Hydrochloric acid):
HCl is a strong acid. When dissolved in water, it undergoes virtually complete ionization (dissociation) into hydrogen ions and chloride ions according to the equation:
$H\mathrm{Cl}\left(\mathrm{aq}\right)\to H^{+}\left(\mathrm{aq}\right)+{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)$
Because it dissociates completely, it produces a high concentration of free ions in solution, making it a strong electrolyte and an excellent conductor of electricity.

2. CH₃COOH (Acetic acid):
CH₃COOH is a weak acid. It only partially ionizes in aqueous solution, leaving most of the acid as molecules:
${\mathrm{CH}}_3\mathrm{COOH}\left(\mathrm{aq}\right)\rightleftharpoons {\mathrm{CH}}_3{\mathrm{COO}}^{-}\left(\mathrm{aq}\right)+H^{+}\left(\mathrm{aq}\right)$
Since the concentration of ions is very low, it is a weak electrolyte and a poor conductor compared to strong acids.

3. NH₃ (Ammonia):
NH₃ is a weak base. In water, it reacts partially to form ammonium and hydroxide ions:
${\mathrm{NH}}_3\left(\mathrm{aq}\right)+H_{2}O\left(l\right)\rightleftharpoons {{\mathrm{NH}}_4}^{+}\left(\mathrm{aq}\right)+{\mathrm{OH}}^{-}\left(\mathrm{aq}\right)$
Like acetic acid, it only partially dissociates, resulting in low ion concentration and weak electrical conductivity.

4. C₆H₁₂O₆ (Glucose):
C₆H₁₂O₆ is a covalent organic compound (a sugar). When dissolved in water, it does not dissociate into ions at all; it remains in molecular form:
$C_6{H}_{12}{O}_6\left(s\right)\to C_6{H}_{12}{O}_6\left(\mathrm{aq}\right)$
Because there are no free ions produced, it is a non-electrolyte and does not conduct electricity.

Conclusion:
Since HCl is the only strong electrolyte among the options and dissociates completely into ions, its aqueous solution has the highest concentration of mobile charge carriers and is therefore the best conductor of electricity.