In this direct and indirect speech question, convert the coach instruction “Do not make the water muddy” to the correct indirect form by choosing the most appropriate alternative.

Introduction / Context:
This question tests knowledge of converting imperative sentences from direct speech to indirect speech. The original direct speech sentence is of the form The coach said to the child, Do not make the water muddy. In indirect speech, we no longer quote the exact words but report the instruction in a grammatically correct reporting structure. Mastering this transformation is essential for accurate narration in written English and frequently appears in competitive exams.

Given Data / Assumptions:
The given material includes:

• Speaker: the coach.
• Listener: the child.
• Direct command: Do not make the water muddy.
• Reporting verb in the options: commanded.
• The sentence is negative and imperative in form.

Concept / Approach:
When we change a negative imperative sentence from direct to indirect speech, we use a reporting verb like told, ordered, or commanded, and then use the structure not to plus base verb. The phrase Do not make the water muddy becomes not to make the water muddy. The preposition to should follow the reporting verb with the object of the command, so we write commanded the child, not commanded to the child. We also convert muddy to dirty in the options, which is an acceptable synonym and does not change the core meaning.

Step-by-Step Solution:
Step 1: Identify the type of sentence in direct speech. It is an imperative command with not. Step 2: Choose an appropriate reporting verb for a command, such as commanded. Step 3: In indirect speech, the structure should be commanded plus object plus not to plus base form of the verb. Step 4: Place the object immediately after the reporting verb: commanded the child. Step 5: Convert Do not make the water muddy to not to make the water dirty, keeping the negative instruction. Step 6: Combine the parts to obtain: The coach commanded the child not to make the water dirty.

Verification / Alternative check:
Check each option against the rules. Option c, The coach commanded the child not to make the water dirty, follows the pattern commanded plus object plus not to plus verb plus object and gives a clear reported command. Option b, commanded to the child not to make the water dirty, wrongly uses commanded to the child, which is not standard collocation. Options a and d keep do not in the reported part, which is incorrect for indirect speech in this context. Therefore, option c is the only fully correct transformation.

Why Other Options Are Wrong:
Option a is wrong because it uses the direct speech form do not inside a reported clause, which is not the standard way to report a command. Option b is incorrect as the phrase commanded to the child is not idiomatic; the object of the command should follow directly without the preposition. Option d combines both issues, using commanded to the child and keeping do not in a way that does not match indirect speech rules. These options fail to apply the correct not to plus base verb structure.

Common Pitfalls:
A common mistake is to keep the exact wording of the command after the reporting verb, forgetting that indirect speech requires a change in structure. Another pitfall is the misuse of prepositions, such as adding to after commanded or ordered when the object should directly follow. Learners should memorise the standard pattern for reporting negative commands: subject plus reporting verb plus object plus not to plus base form of the main verb.

Final Answer:
The correct indirect speech form is The coach commanded the child not to make the water dirty.