Consider the reaction sequences:$3\text{ROH}+{\text{PCl}}_3\to 3\text{RCl}+A$$\text{ROH}+{\text{PCl}}_5\to \text{RCl}+\text{HCl}+B$ What are A and B?

1. A
   ${\text{POCl}}_3$ and ${\text{H}}_3{\text{PO}}_4$
2. B
   ${\text{H}}_3{\text{PO}}_4$ and ${\text{POCl}}_3$
3. C
   ${\text{H}}_3{\text{PO}}_3$ and ${\text{POCl}}_3$
4. D
   ${\text{POCl}}_3$ and ${\text{H}}_3{\text{PO}}_3$