Which one of these represents diversifiable risk?

Red Bull co-founder and F1 team owner Dietrich Mateschitz dies at 78

US stocks and Treasuries fall after hawkish comments from Fed official

US oil prices fall 10% in the week as demand worries rise

Top Fed official warns US unemployment could hit 5% next year

One CEO sold about 40% of the shares he owned in his company at a high point, making a $36 million profit. One week later, the company started releasing a string of negative announcements. Over three months, the stock price dropped 60%. The CEO could not have earned such a profit if the market was

weak form efficient.

semi-strong form efficient.

semi-weak form efficient.

strong form efficient.