Step 1: Recall Faraday's law.
When the magnetic flux through a coil changes, a voltage called e.m.f. appears across it. The size is $E=N\frac{\Delta\phi}{\Delta t}$, where $N$ is the number of turns, $\Delta\phi$ is the flux change, and $\Delta t$ is the time taken. We use it because the flux here is changing in time.
Step 2: Note why turns matter.
Each turn of wire feels the same flux change, so $N$ turns multiply the effect. That is why $N$ sits in front of the formula.
Step 3: Write the given values.
The coil has $N=20$ turns. The flux starts at $\phi_i=0.3\,\text{Wb}$ and drops to $\phi_f=0$, over a time $\Delta t=1\,\text{s}$.
Step 4: Find the flux change.
The change in flux is the start value minus the end value. \[ \Delta\phi=0.3-0=0.3\,\text{Wb} \]
Step 5: Put values into the formula.
Substitute the numbers. \[ E=20\times\frac{0.3}{1} \]
Step 6: Compute the e.m.f.
Multiply it out. \[ E=20\times 0.3=6\,\text{V} \] So the induced e.m.f. is $6\,\text{V}$, which is option 2. \[ \boxed{6\ \text{V}} \]