The correct option to fill in the blank in the sentence "Every time you pay a bill you must insist .... being given a receipt" is C. on. Step-by-Step Explanation:

1. Understanding the Phrase: The phrase "insist on" is a common English expression. It means to demand something firmly or to make a strong request for something. In this context, when you pay a bill, you are strongly requesting or demanding to receive a receipt.
2. Usage of "Insist": The verb "insist" is typically followed by the preposition "on" when it is used in this context. For example, you might say:
3. "I insist on having a receipt."
4. "She insisted on being treated fairly."
5. Grammatical Structure: The structure of the sentence requires a preposition that correctly links the verb "insist" to the action of "being given a receipt." The preposition "on" fits this structure perfectly, as it indicates the subject's insistence regarding a specific action or condition.

Why the Other Options Are Incorrect:

• A. in: The phrase "insist in" is not a standard English expression. While "in" can be used in other contexts (e.g., "insist in doing something"), it does not work with "insist" when referring to demanding something. Therefore, this option is incorrect.
• B. from: The phrase "insist from" is also not correct. "From" typically indicates a source or origin, and it does not convey the meaning of demanding or requesting something. Thus, this option does not fit the context of the sentence.
• D. by: The phrase "insist by" is not commonly used in English. "By" usually indicates a method or means of doing something, which does not align with the meaning of demanding or requesting a receipt. Therefore, this option is also incorrect.

Summary of Key Points:

• The correct answer is C. on because "insist on" is the appropriate phrase to express a strong demand for something.
• "Insist" requires the preposition "on" when followed by a noun or gerund (e.g., "being given a receipt").
• The other options (A, B, D) do not fit grammatically or contextually with the verb "insist."

Revision Summary:

• "Insist on" is the correct phrase to use when demanding something.
• The sentence requires a preposition that links the verb to the action of receiving a receipt.
• Options A, B, and D do not fit the context or grammatical structure of the sentence.
• Always remember the common phrases associated with verbs to avoid confusion in similar questions.