Sentence Correction

Diabetes, together with its serious complications, ranks as the nation's third leading cause of death, surpassed only by heart disease and cancer
(a) ranks as the nation's third leading cause of death, surpassed only
(b) rank as the nation's third leading cause of death, only surpassed
(c) has the rank of the nation's third leading cause of death, only surpassed
(d) are the nation's third leading causes of death, surpassed only
(e) have been ranked as the nation's third leading causes of death, only surpassed

The subject of the sentence is DIABETES. "together with is serious complications" is a modifying phrase (modifying phrases are often offset by commas). Don't make the mistake of thinking that the subject must be the nearest noun. "Complications" was an object of the preposition "with."

Since "diabetes" is a singular name of a disease (and in case we were wondering whether it was singular or plural, the GMAT was nice enough to give us the singular pronoun "it"), we need a singular verb. B, D, and E all have plural verbs, so eliminate those. In C, "has the rank of" is not idiomatically correct. The answer is A.

If you're having trouble figuring out what the core of the sentence (SUBJECT + VERB) is, these articles should help:
https://www.manhattanprep.com/gmat/blog ... ce-part-1/
https://www.manhattanprep.com/gmat/blog ... -part-2-2/
https://www.manhattanprep.com/gmat/blog ... -part-iii/
https://www.manhattanprep.com/gmat/blog ... ce-part-4/