5 exercises — practise substituting 'one'/'ones' for previously mentioned nouns, and knowing when not to.
0 / 5 completed
1 / 5
Which sentence correctly uses "one" to avoid repeating a previously mentioned countable noun?
"One" substitutes for a previously mentioned singular countable noun ("endpoint") when a modifier ("new") is added, avoiding awkward repetition. Option B is correct: "created a new one" = "created a new endpoint". Option A repeats "endpoint" verbatim, which is grammatical but more repetitive than necessary in fluent writing. Option C incorrectly uses "it", which substitutes for the exact same specific referent, not a new, different instance of the same category — "it" would wrongly imply the team recreated the very same old endpoint. Option D omits the noun/pronoun entirely after the adjective "new", which is ungrammatical — English requires either the noun or a substitute pronoun after a standalone modifying adjective in this position.
2 / 5
Which sentence correctly uses "ones" (plural) to avoid repeating a plural countable noun?
"Ones" is the plural form of the substitute pronoun "one", used here to stand in for "test cases" after the modifier "more reliable". Option B is correct: "more reliable ones" = "more reliable test cases". Option A repeats the full noun phrase, which is grammatical but wordier. Option C incorrectly uses singular "one" for a plural referent — number agreement is required between the substitute pronoun and what it replaces. Option D incorrectly uses "it", a pronoun for a single, specific, already-fully-identified referent, not a substitute for "several new instances of a category" — "it" cannot pluralize or take modifiers like "more reliable" in this way.
3 / 5
Which sentence demonstrates a case where "one" substitution is NOT appropriate, and the full noun (or no substitute) should be used instead?
Option C is the incorrect substitution: "the client expects one" is ambiguous and unnatural because "JSON" here is used as an uncountable mass/format noun in this context (referring to a data format, not a countable single item), so "one" does not felicitously substitute for it — the correct sentence would be "the client expects it" (referring back to the JSON response) or restate the noun ("the client expects a JSON response"). Options A, B, and D all correctly use "one" to replace a clearly countable singular noun already established in context (library, algorithm, version) that is being contrasted or modified. "One" substitution works well for countable nouns with a modifier or determiner, but not for uncountable/mass nouns or abstract references like a data format used generically.
4 / 5
Which sentence correctly uses "the one" (with a definite article) versus "one" (indefinite) to refer back to a specific, previously identified item?
"The one" is used with a definite article when referring to a specific, identifiable member of a previously mentioned set, especially when followed by a defining relative clause ("that failed CI"). Option A is correct: "the one that failed CI" picks out the single specific branch matching that description. Option B is ungrammatical — "a" and "the" cannot both function this way; "a one" is not standard usage in this pattern. Option C ("one that failed") lacks the definite article, which changes the meaning to something closer to "some unspecified branch", losing the sense of picking out the single, specific branch already implied by the singular verb "was" later in the sentence. Option D incorrectly pluralizes to "ones" while the rest of the sentence (singular verb "was") requires a singular referent — a number-agreement mismatch.
5 / 5
Which sentence correctly avoids using "one" where simple ellipsis (omitting the noun entirely) is more natural in technical English?
When two parallel noun phrases share the same head noun in a list or coordination, English often prefers simple ellipsis (dropping the repeated noun entirely) over inserting "one". Option B is correct and most natural: "staging and production" (both understood as "environments"), with the shared noun omitted rather than substituted. Option A incorrectly attaches "one" only to the second item, creating an asymmetric, awkward construction. Option C is grammatical but unnecessarily wordy and slightly odd-sounding for a simple list — "one" substitution is more natural when a modifier distinguishes the items (as in earlier examples: "a new one", "more reliable ones") than in a plain coordinated list like this. Option D adds definite articles that are not appropriate for introducing a list of environment types generically.