Which of the following would be considered a pure risk event?

A pure risk event is defined as a situation that can lead to a loss or no loss but does not present an opportunity for financial gain. In this context, experiencing a house fire exemplifies pure risk because it can result in significant property damage and a potential loss of personal belongings. On the other hand, there is no chance of profit; the outcome is strictly negative or neutral.

The other scenarios presented reflect different types of risks. Investing in stocks and starting a new business incorporate the possibility of both loss and gain, categorizing them as speculative risks rather than pure risks. Similarly, buying a lottery ticket is also characterized by its potential for financial gain albeit with a significant risk of loss, thus making it speculative as well. Therefore, the correct answer, experiencing a house fire, aligns perfectly with the definition of a pure risk event.