Hello there!
Your question asks what kind of actions the people took with the stocks.
Answer: C). Insider trading
The reason why answer choice "C). Insider trading" is the correct answer is because the person is performing actions that can lead to automatic success in the stock market.
Insider trading is getting the knowledge of a business or company before hand and making changes to one's stocks in order to keep making profit. People do insider trading in order to have an advantage with their stocks with information that is confidential. Insider trading is ILLEGAL and will result in time in prison, and will also have criminal fines.
Let me explain insider trading for you in an example. For example, Bob has stocks from Samsung, he found information that Samsung has been having a rough time keeping their business higher than Apple, so he sells his Samsung stocks before the stock value decreases. He would be performing insider trading because he used information from the business in order to sell his stocks before the stock value decreases, and that will cause him to lose money if he doesn't sell it.
In your question, people got the information that the Pizza place was purchased by a nationwide pizza place, which means that the stock will increase its value. Therefore, with the information they got, they bought a stock from the Italian Stallion Pizza Stations before the stock price increases because they know they'll make profit from it, due to the information that they heard on the plane.
I hope this helps!
Best regards, MasterInvestor