Answer : The correct option is D.
Explanation :
The rules for naming of binary molecular compound :
In the given formula, the lower group number element is written first in the name and keep its element name and the higher group number is written second.
First element in the formula is named first and keep its element name.
Second element is named second.
Therefore, the chemical name of compound [tex]P_4O_9[/tex] is Tetra-phosphorous nonoxide.