In the following sentence, identify the part that contains an error: “He put the birds softly, one by one, interior their warm little home.”

Introduction / Context:
This question asks you to locate the grammatical or lexical error in a sentence about gently placing birds back into their home. The sentence is split into three numbered parts and a fourth option indicating no error. The main task is to identify the incorrect preposition or word choice and understand why it is wrong.

Given Data / Assumptions:
The sentence is divided as follows:
- Part (1): He put the birds softly,
- Part (2): one by one, interior their
- Part (3): warm little home.
- Part (4): No Error.
We assume that the intended meaning is “He put the birds softly, one by one, into their warm little home.”

Concept / Approach:
The phrase “interior their” is ungrammatical and unnatural in English. The correct preposition to show movement towards the inside of a place is “into”. Therefore, we expect “into their warm little home” rather than “interior their warm little home”. The rest of the sentence uses correct adverbs and adjectives, so the error is clearly with the word “interior”.

Step-by-Step Solution:
Step 1: Examine part (1): “He put the birds softly,”. This is acceptable; “softly” describes the gentle manner in which he put the birds. Step 2: Examine part (2): “one by one, interior their”. The phrase “one by one” is fine, but “interior their” is not a valid prepositional expression in English. Step 3: Recognise that “interior” is typically a noun or adjective, not a preposition. The sentence obviously needs a preposition of movement. Step 4: Replace “interior” with “into”: “one by one, into their warm little home.” This corrected phrase is idiomatic and grammatically correct. Step 5: Examine part (3): “warm little home.” This phrase is fine as it stands, with adjectives “warm” and “little” correctly placed before the noun “home”. Step 6: Therefore, the error lies entirely in part (2).

Verification / Alternative check:
Read the revised whole sentence: “He put the birds softly, one by one, into their warm little home.” This now sounds completely correct and natural. Since only part (2) required modification, the answer must be the label corresponding to that part.

Why Other Options Are Wrong:
- Part (1): contains no grammatical error. The adverb “softly” is properly used after the verb phrase “put the birds”.
- Part (3): is a perfectly grammatical noun phrase; “warm little home” is standard English.
- Part (4): selecting “No Error” would ignore the obvious misuse of “interior” in part (2).

Common Pitfalls:
Some test takers may overlook the wrong word if they read too quickly, focusing instead on verb tenses or subject-verb agreement. However, vocabulary and preposition errors are very common in such questions. Always read each part slowly and see whether a simple, idiomatic alternative would fit better. In expressions of movement into a place, “into” is far more common than any complicated substitute.

Final Answer:
The incorrect part is (2); “interior their” should be corrected to “into their”.