17.) use sentence 1.
ragtime
adjective
adverb
preposition
noun **
18.) use sentence 2.
until
adjective
adverb
preposition **
noun
19.) use sentence 3.
ragtime
adjective ***
adverb
preposition
noun
20.) use sentence 4
and
noun
pronoun
conjunction **
adverb
21.) use sentence 5.
cakewalk
noun
pronoun
verb
adverb***
sentence 1.) ragtime* is one of the ancestors of jazz
sentence 2.) it was popular from the 1890s until* the end of the first world war.
sentence 3.) in ragtime* music, melodies are syncopated
sentence 4.) the style derived from street bands in new orleans, st. louis, and* memphis.
sentence 5.) it was related to a popular dance at the turn of the century called the "cakewalk".*
96 pts

The function of given words in the different sentences provided would be as follows:

17). - d). Noun

18).  - c). Preposition

19).  - a). Adjective

20). - c). Conjunction

21).  - a). Noun

17). Noun are described as the words that are employed to refer to the name of an individual, object, etc.

Since 'Ragtime' in sentence 1 denotes the name of a style or pattern of music, it would be considered as a 'noun.'

18). Prepositions are the words that denote association of a noun, noun's referrent(pronoun), or even phrases to the sentence's other components.

In sentence 2, 'until' is linking the phrase 'the end...War' to the previous part of the sentence, it is the preposition.

19). Adjectives are the words that are used only to add detail or description to the sentence by qualifying a noun.

In the sentence 3, 'ragtime' is the adjective as it modifies 'music,' the noun, by adding description about it.

20). Conjunction are characterized the expressions that help link two words, clauses, or often phrases in a sentence.

'And' in the sentence 4 is joining the two band names 'New Orleans' and 'Memphis' and hence, it is the conjunction.

21). In the sentence 5, 'cakewalk' is the noun at the object's place that give the name to the famous dance style towards the century's end.

Learn more about 'Parts of Speech' here:

link

17. Ragtime-Noun.

18. Until-Preposition.

19. Ragtime-Adjective.

20. And-Conjunction.

21. Cakewalk-Noun.

thats just how it be sometimes