A vibration magnetometer placed in magnetic meridian has a small bar magnet. The magnet executes oscillations with a time period of $2\text{ sec}$ in earth's horizontal magnetic field of $24\text{ microtesla}$. When a horizontal field of $18\text{ microtesla}$ is produced opposite to the earth's field by placing a current carrying wire, the new time period of magnet will be:

1. A
   $4\text{ s}$
2. B
   $1\text{ s}$
3. C
   $2\text{ s}$
4. D
   $3\text{ s}$