Answer:
D. Formal
Explanation:
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HMH books
Its on the site.
Neither
An indefinite adjective is used to describe a noun in a non-specific sense. The most common indefinite adjectives are any, each, few, many, much, most, several, and some. --- (grammar-monster.com)
1a. (advocate)
1b. (exploit)
2a. (innovative)
2b. (hub)
3a. (indebted)
3b. (spearhead)
4a. (estimate)
4b. (documentary)
