Choose the correct phrase to complete the sentence: She is not used ____ for so long.

Introduction / Context:
This sentence-improvement question tests your understanding of the expression “to be used to” and the verb form that should follow it. The sentence given is: “She is not used (to sleep) for so long.” You must choose the option that produces a natural and grammatically correct sentence in standard English.

Given Data / Assumptions:

• Main clause: “She is not used … for so long.”
• The underlined phrase in the exam: “to sleep”.
• Options: “to be sleeping”, “to sleep”, “to sleeping”, and “No improvement”.
• The context implies that long periods of sleep are not normal or habitual for her.

Concept / Approach:
English distinguishes between “used to do something” (past habit) and “be used to something” (be accustomed to something). After “be used to”, we use a noun or a gerund (verb + ing): “She is used to noise”, “He is used to working late.” In this question, “is not used to …” clearly belongs to the second pattern, meaning “is not accustomed to”, so the correct completion should be a gerund: “sleeping so long”.

Step-by-Step Solution:
Step 1: Identify the structure: “She is not used to …” expresses a lack of habit or familiarity with something. Step 2: Recall the rule: after “be used to”, we use a noun or gerund (verb + ing), not the bare infinitive. Step 3: Examine option C “to sleeping”. If we expand the sentence, it becomes “She is not used to sleeping for so long”, which is correct and idiomatic. Step 4: Option B “to sleep” would work with the pattern “used to + verb” in the sense of past habit (e.g., “She used to sleep for so long”), but that is a different structure and meaning. Step 5: Option A “to be sleeping” sounds unnatural in this context and suggests a specific moment rather than a general habit. Step 6: “No improvement” would keep the incorrect pattern “used to sleep” after “is”, mixing the two structures. Step 7: Therefore, the correct improvement is “to sleeping”.

Verification / Alternative check:
Compare the two patterns side by side: Pattern 1 (past habit): “She used to sleep for so long” (no auxiliary “is”; describes what she did regularly in the past). Pattern 2 (accustomed to): “She is used to sleeping for so long” (describes what she is accustomed to now). In our sentence, we already have the verb “is”, so we are clearly in Pattern 2. Therefore, “to + gerund” is required, supporting “to sleeping” as the correct choice.

Why Other Options Are Wrong:
to be sleeping: grammatically possible in some contexts but awkward and not the standard pattern with “is used to” for habits. to sleep: belongs to the “used to + verb” pattern of past habits, which conflicts with the “is not used to” structure in the sentence. No improvement: leaves the sentence in a mixed and incorrect form.

Common Pitfalls:
Many learners confuse “used to do” with “be used to doing”. The first refers to a former habit (“I used to play cricket”), while the second refers to present familiarity or comfort (“I am used to playing cricket in hot weather”). Mixing these structures leads to errors. The safest strategy is to check whether “am/is/are/was/were” appears before “used”; if it does, then “to” is a preposition and must be followed by a noun or gerund.

Final Answer:
The correct improvement is to sleeping, making the sentence “She is not used to sleeping for so long.”