For the reversible reaction 

${\mathrm{N}}_{2\left(g\right)}+3{\mathrm{H}}_{2\left(g\right)}\rightleftharpoons 2{\mathrm{NH}}_{3\left(g\right)}+\text{ heat }$

The equilibrium shifts in forward direction

• A

  By increasing the concentraction of ${\mathrm{NH}}_{3\left(\mathrm{g}\right)}$

• B

  by decreasing the pressure

• C

  By decreasing the concentrations of ${\mathrm{N}}_{2\left(g\right)}\text{ and }{\mathrm{H}}_{2\left(g\right)}$

• D

   by increasing pressure and decreasing temperature.