Answer:
The noun phrase that completes the sentence is A. , a relatively rare event,: A total solar eclipse, a relatively rare event, causes a change in the amount of visible light.
Step-by-step explanation:
A noun phrase is a group of words in a sentence that act together as a noun. In this way, the noun phrase can act as object, subject, prepositional object or apposition, like in this case. Therefore, option A is the correct answer.