The question statement is incomplete: the field expressions for options A, B, C, and D are missing.

To determine which expressions are allowed for a plane electromagnetic wave propagating along the positive $Y$-direction, we must check the following conditions for each option:

1. Direction of propagation For a wave traveling along $+Y$, the phase must be of the form $ky-\omega t$ (or any equivalent form such as $\omega t-ky$ inside sine/cosine).

2. Mutual perpendicularity The electric field $\vec E$ and magnetic field $\vec B$ must be perpendicular to each other and also perpendicular to the direction of propagation. Since propagation is along $\hat y$, both $\vec E$ and $\vec B$ must lie in the $xz$-plane.

3. Right-hand rule / Poynting vector direction The propagation direction is given by $\vec S \propto \vec E \times \vec B$ so we need $\vec E \times \vec B = +\hat y.$

4. Magnitude relation For an electromagnetic wave, $E_0 = cB_0.$

5. Intensity relation If intensity is $I$, then in vacuum $I = \frac{1}{2}c\varepsilon_0 E_0^2 = \frac{1}{2}\frac{c}{\mu_0}B_0^2.$

Because the actual expressions in options A, B, C, and D are not provided, it is impossible to verify which one satisfies all these conditions.

So, although the stored correct answer is marked as A, I cannot independently confirm it from the given data.

If you send the missing field expressions for options A–D, I can evaluate them one by one and give the final verified answer.