In an English sentence improvement item, choose the best alternative to correct the underlined part in the sentence: "She has no pen to write."

Introduction / Context:
This sentence improvement question tests the correct use of a preposition after the verb "write" when we are referring to an instrument used for writing. The original sentence "She has no pen to write" sounds incomplete and slightly unnatural. The goal is to choose the option that completes the sense correctly, making the sentence idiomatic and clear.

Given Data / Assumptions:

• Original sentence: "She has no pen to write."
• The underlined part is "to write".
• Options: write with, write at, write in, No improvement.
• The intended meaning is that she does not have a pen available as an instrument for writing.

Concept / Approach:
When we talk about the instrument used for a particular action, English typically uses "with". For example, "write with a pen", "cut with a knife", or "draw with a pencil". Therefore, the correct prepositional phrase after "pen" should be "to write with", indicating the purpose of the pen as a tool. The other options either do not fit this purpose or are used for different types of complements.

Step-by-Step Solution:
Step 1: Identify the idea: the pen is an instrument that would be used for writing. Step 2: Recall the common pattern: "write with a pen", "write with a marker". Step 3: Substitute "write with" into the original sentence: "She has no pen to write with." This is natural and grammatically correct. Step 4: Test "write at": "She has no pen to write at" is incorrect and does not fit English usage. Step 5: Test "write in": We say "write in ink" or "write in a notebook", but not "pen to write in". The object of "in" is usually a medium or container, not the instrument itself. Step 6: Test "No improvement": Keeping "to write" alone leaves the sentence sounding incomplete and less idiomatic.

Verification / Alternative check:
You can verify by comparing similar structures: "He has no knife to cut with", "They have no tools to work with", and "I have no brush to paint with." In these sentences, "with" clearly marks the instrument. Grammar references also emphasise that "with" is the standard preposition used to indicate the tool or instrument used to perform an action. Therefore, "write with" is the correct phrase.

Why Other Options Are Wrong:

• write at: Usually used with locations or targets, such as "write at the top of the page". It does not refer to the instrument.
• write in: Used with mediums or languages, as in "write in ink" or "write in English", but this does not match the structure with "pen".
• No improvement: The original "to write" does not clearly show the instrumental function of the pen and sounds incomplete.

Common Pitfalls:
Some learners are tempted to leave the sentence as it is because it is somewhat understandable. However, exam standards require precise and idiomatic English. Others may mistakenly choose "write in" because they have seen it used with ink or languages. Focusing on the role of the noun after the verb (instrument versus medium) will help you choose the correct preposition in such questions.

Final Answer:
The improved sentence is: "She has no pen to write with."