A $\mathrel{\mathop{\kern0pt\longrightarrow} \limits_{}^{573\,K}}$ Red phosphorus $$\mathrel{\mathop{\kern0pt\longrightarrow} \limits_{under\,pressure}^{heat\,;\,803\,K}} $$ B

Red phosphorus is obtained by heating "A" at 573 K, and can be converted to "B" by heating at 803 K under pressure.

A and B, respectively, are

1. A $\beta$-black phosphorus and white phosphorus.
2. B white phosphorus and $\beta$-black phosphorus.
3. C $\alpha$-black phosphorus and white phosphorus.
4. D white phosphorus and $\alpha$-black phosphorus. Correct answer