1. Use the interference intensity formula

For two coherent sources with intensities $I_1$ and $I_2$, the resultant intensity is

$I = I_1 + I_2 + 2\sqrt{I_1 I_2}\cos\phi$

where $\phi$ is the phase difference.

2. Given data

$I_1 = I_2 = I_0$

So,

$I = I_0 + I_0 + 2\sqrt{I_0\cdot I_0}\cos\phi$

$I = 2I_0 + 2I_0\cos\phi$

3. Condition for minima

At minima, $\cos\phi = -1$.

Thus,

$I_{\min} = 2I_0 - 2I_0 = 0$

This matches the given statement that intensity at minima is zero.

4. Condition for maxima

At maxima, $\cos\phi = 1$.

Thus,

$I_{\max} = 2I_0 + 2I_0 = 4I_0$

5. Check options

• A: $I_0$ — incorrect
• B: $2I_0$ — incorrect
• C: $5I_0$ — incorrect
• D: $4I_0$ — correct

Therefore, the intensity at maxima is

$\boxed{4I_0}$