The simple predicate in the sentence "The nurse in the white uniform arrived at the hospital just in time" is D. arrived.
The simple predicate is the main verb or verb phrase in a sentence. In other words, the simple predicate indicates what the subject is doing and it is different from the complete predicate, which includes the verb/verb phrase and also the modifiers. In order to identify the simple predicate it is important to ask ourselves what the subject does or is. In the case of this sentence, the verb "arrived" is what indicates what the nurse did; therefore, "arrived" is the simple predicate.