In this sentence improvement item, choose the correct phrase to replace the bracketed expression "(locked at)" in the sentence about privatising the airline and freeing funds for education and health.

Introduction / Context:
This question tests your understanding of common English collocations used in economic and policy discussions. The sentence describes a proposal to privatise an airline and free funds for education and health that are currently tied up in the public sector. The bracketed phrase "locked at" is not idiomatic, so you must choose the option that correctly expresses the idea that funds are stuck or unavailable for other uses.

Given Data / Assumptions:

• The sentence talks about a compelling case for privatising an airline.
• The key idea is freeing funds that are currently not available for education and health.
• The bracketed phrase is "locked at".
• Options include "locked of", "locked on", "locked up", and "No improvement".

Concept / Approach:
In economic and everyday English, the phrase "locked up" is used to describe capital or funds that are tied up in a particular asset or investment and cannot be easily used elsewhere. Expressions such as "capital locked up in real estate" or "funds locked up in loss making public sector units" are very common. The phrase "locked at" does not carry this meaning and is therefore incorrect. You have to select the option that gives the standard collocation for money that is stuck in a particular place.

Step-by-Step Solution:
Step 1: Focus on the meaning: funds are not free; they are tied into the airline. Step 2: Recall the common phrase "locked up funds" used in financial contexts. Step 3: Replace "locked at" with "locked up" to create "freeing locked up funds". Step 4: Read the full sentence with this phrase to ensure it sounds natural. Step 5: Verify that no other option gives the correct financial meaning.

Verification / Alternative check:
Insert each option into the sentence and test: "freeing locked of funds" is ungrammatical; "freeing locked on funds" does not convey that money is stuck; "freeing locked up funds" clearly suggests releasing money that is tied up in the airline. The version with "locked up" also matches how newspapers and economic analysts typically write about public assets and privatisation. Therefore, "locked up" is the only acceptable improvement.

Why Other Options Are Wrong:
"Locked of" is grammatically wrong; the preposition "of" cannot follow "locked" in this structure.

"Locked on" suggests a focus or attention fixed on something, not funds tied into an asset.

"No improvement" is incorrect because "locked at" is not idiomatic and does not express the idea of funds being tied up.

Common Pitfalls:
Students sometimes try to guess based on the preposition alone, without thinking of complete expressions used in real financial language. A good strategy is to learn typical collocations such as "tied up capital", "locked up funds", and "frozen assets". Once you recognise "locked up" as a standard phrase, it becomes easy to pick it over unnatural combinations like "locked at".

Final Answer:
The correct improvement is "locked up", giving the sentence: privatising the airline and freeing locked up funds for education and health.