In the same grammar passage, choose the correct preposition to complete the phrase "forms a distinct part _____ a composition, paragraph, or discourse".

Introduction / Context:
This question continues the passage about phrases and clauses in English grammar. The sentence explains that a clause "forms a distinct part _____ a composition, paragraph, or discourse". The blank must be filled with the correct preposition so that the phrase sounds natural and grammatically accurate. Prepositions such as "of", "in", "for", "at" and "to" often create confusion because they can sometimes follow the same verb but with different meanings. Recognising common fixed expressions is therefore a key skill tested here.

Given Data / Assumptions:

• The fragment to be completed is "forms a distinct part _____ a composition, paragraph, or discourse".
• The options are "for", "at", "of", "to" and "in".
• The subject being described is "a clause", and the sentence wants to show its relation to a composition.
• We assume standard formal English usage as found in grammar explanations.

Concept / Approach:
In English, we commonly use the phrase "part of" to show that something is a component or segment of a larger whole. For example, we say "part of the book", "part of the plan" or "part of the course". Here, a clause is being described as a "distinct part" of a composition, paragraph or discourse. The most natural and idiomatic preposition after "part" in this context is "of". The approach is to test each candidate preposition in the phrase and choose the one that fits known patterns of usage.

Step-by-Step Solution:
Step 1: Focus on the expression "a distinct part _____ a composition". Step 2: Recall familiar collocations like "part of a whole", "part of a family" and "part of a story". Step 3: Insert "of" and read the phrase: "forms a distinct part of a composition, paragraph, or discourse". This sounds natural and correct. Step 4: Test other prepositions briefly and notice that they do not form common expressions with "part" in this sense.

Verification / Alternative check:
Read the full sentence from the passage: "It differs from the clause, which is a short sentence that forms a distinct part of a composition, paragraph, or discourse." This full sentence is clearly what a grammar text would use to define a clause. If we tried "for", the phrase would become "part for a composition", which suggests purpose rather than membership. "At" would give "part at a composition", which is not idiomatic. "To" would suggest direction, and "in" would imply location, none of which describe the relationship of a clause to a composition. Therefore, the only preposition that expresses a correct part to whole relationship is "of".

Why Other Options Are Wrong:
"For" is often used to show purpose or benefit, such as "tools for work", not membership in a whole. "At" is used with places, times or activities, such as "at school" or "at noon". "To" mainly shows direction or relation, for example "go to the park". "In" shows location or inclusion, such as "in the box". None of these create the fixed phrase "part for", "part at", "part to" or "part in" when we talk about a component of a larger unit. As a result, these prepositions do not convey the intended grammatical relationship between clause and composition.

Common Pitfalls:
Many learners confuse "of" and "in" because both can show some kind of connection. However, "part of" is the standard collocation when something belongs to a bigger whole. Overthinking and searching for more complex structures can also lead to errors, when the simple and familiar phrase is actually the correct one. A useful habit is to remember collocations as complete chunks, for example "member of", "piece of", "part of", and to recall them quickly when you see similar structures in exam questions.

Final Answer:
The correct preposition is of, so the phrase should read "forms a distinct part of a composition, paragraph, or discourse".