What is defined as "insider trading"?

Insider trading is defined as the buying or selling of a company's stock or other securities based on material information that is not publicly available. This non-public information could have a significant impact on the company's stock price if it were to be disclosed. This definition encapsulates why option C is correct; it highlights the essential element of utilizing undisclosed information to gain an advantage in the securities market, thereby violating ethical and legal standards.

The concept of insider trading is critical in maintaining the integrity of financial markets, as it ensures that all investors operate on a level playing field, with equal access to important information. This prevents unfair advantages and promotes trust in the financial system.

In contrast, the other options describe scenarios that do not fit the definition of insider trading. Trading while under a corporate mandate typically refers to transactions that comply with company policies and regulations, often aimed at avoiding conflicts of interest. Trading based on public information does not involve any unethical advantage since the information is accessible to all market participants. Lastly, trading without client consent pertains to the fiduciary duties of financial advisors and is more about ethical responsibility to clients rather than the legality surrounding access to non-public information.