Another possible diagnosis included pulmonary embolus.

Verb/Verbs

Answer:
diagnosis

Nope.

Diagnosis is a noun, the subject of the sentence.

Check the other words in a dictionary to find the verb.

I checked all the other words in a dictionary (should have done that first) and my answer is:

Sentence:
Another possible diagnosis included pulmonary embolus.

Verb = included
Adjective = another - possible
Noun = diagnosis

Yay! You've got it!

The verb in the sentence is "included."