Correct Answer: Iconoclast

Solution : The correct choice is the first option.

Explanation:
Iconoclast: This term refers to a person who challenges or opposes established traditions, beliefs, or institutions, often by attacking or criticising them. They aim to bring about change or reform by challenging existing norms.

The meanings of the other options are as follows:

• Impregnable: This term refers to something unable to be overcome or penetrated.
• Immoral: This term refers to actions or behaviours, not in line with accepted principles of right and wrong and are often considered unethical or sinful.
• Insolvent: This term describes a person or entity that is unable to pay debts or meet financial obligations.

Therefore, the correct answer is iconoclast.