A longitudinal incision was made along the thenar crease.

Identify parts of speech:

longitudinal = noun
was made = verb
along = preposition
thenar = adjective

Thank You for your help

2, 3, and 4 are correct.

1 is not a noun.

Actually, the identification of parts of speech in the sentence you provided is not completely accurate. Here is the correct breakdown:

longitudinal - adjective (describing the type of incision)
incision - noun (subject of the sentence)
was made - passive verb phrase (describing the action that was done)
along - preposition (showing the relationship between the incision and the thenar crease)
the - definite article (modifying the noun "thenar crease")
thenar - adjective (describing the noun "crease")
crease - noun (object of the preposition "along")

So, the correct identification would be:
longitudinal - adjective
incision - noun
was made - verb phrase
along - preposition
the - article
thenar - adjective
crease - noun

It's important to note that "was made" is not a single verb but a verb phrase consisting of the past tense of the verb "make" (was made).