C.
This is because an adverb is a word that modifies/describes a verb -he sings loudly-, an adjective -very tall-, another adverb -ended too quickly-, or even a whole sentence -Fortunately, I had brought an umbrella-. Adverbs often end in -ly, but some -such as fast- look exactly the same as their adjective counterparts. So, everything but answer C. is actually an adverb.
Hope this helps! I know the other guy answered but I wanted to anyway.
I also just noticed this was asked in 2016 but oops.
Which of the following is the complete predicate?
All except for Jesse and his brother
were finally found
found
Jesse and his brother
Answer:
I believe it's We were drinking water