We said that verbs could either occur by themselves in a VP or with an NP. We captured this fact with the following rule: VP --> V (NP). It is shorthand stating that a VP will contain a verb and optionally will have a NP after it. Now, we have seen that NPs may contain a determiner or not. How can we express that rule? Fill in the blank with the correct formulation indicating that NPs may have a D or may not: NP --> Nom