Step 1: Identify the Word’s Role
Ask: What job does the missing word do in the sentence?
Subject: Who or what performs the action.
Verb: The action or state of being.
Verb complement: Completes the meaning of a verb (object or object complement).
Modifier: Describes or qualifies another element (adjective, adverb, phrase, or clause).
Step 2: Identify the Part of Speech
Every English word belongs to one of 8 categories. Match the part of speech to its possible roles.
1. Noun – names a person, place, thing, or idea.
Roles: subject or object.
Check: singular/plural, count/non-count.
2. Pronoun – replaces a noun.
Roles: subject or object.
Check: count/number agreement; correct case (I/me/my).
3. Determiner – comes before a noun (the, a, this, my, some).
Roles: modifies a noun; cannot stand alone.
Check: definite/indefinite; number/count match.
4. Verb – shows action or state.
Role: predicate of the sentence.
Check: subject–verb agreement; verb types; tense; voice.
5. Adjective – describes a noun or pronoun.
Roles: modifier, subject complement, object complement.
Check: placement, comparative/superlative form.
6. Adverb – modifies verbs, adjectives, or other adverbs.
Role: modifier.
Check: correct form (quickly vs. quick); placement (normal/logical).
7. Preposition – shows relationship (time, place, cause).
Role: part of a prepositional phrase (modifier).
Check: preposition collocation (e.g., responsible for).
8. Conjunction – joins words, phrases, or clauses (and, but, because).
Role: connector, not a sentence element.
Check: logical relationship; parallel structure with “and”.
Application: Official ETS Teacher Set 4
Modern biochemistry focuses on the chemical processes within and related to living organisms. It i_ a laboratory-based sci_ _ _ _ that comb_ _ _ _ biology a_ _ chemistry. Biochemists inves_ _ _ _ _ _ how cells func_ _ _ _ and commu_ _ _ _ _ , exploring t _ _ fundamental mecha_ _ _ _ _ that sus_ _ _ _ life. The field has advanced our understanding of how diseases occur and how they can be treated or prevented. Techniques such as molecular cloning and protein analysis are central to biochemistry, leading to innovations in medicine and biotechnology.
is – verb; agrees with singular subject it.
science – noun; follows article a.
combines – verb; singular subject science → add -s.
and – conjunction; connects two nouns.
investigate – verb; plural subject biochemists → base form.
function – verb; plural subject cells.
communicate – verb; parallel with function.
the – determiner; introduces noun phrase.
mechanisms – plural noun; agrees with plural verb sustain.
sustain – verb; in fixed phrase sustain life.