Which of these risks are most likely systematic as opposed to idiosyncratic?

Which of these risks are most likely systematic as opposed to idiosyncratic?

a. Foreign hackers effectively shut down the internet for weeks

b. A firm's top salesperson is hired away by a competitor

c. A mobile game called Candy Crush becomes a smash hit

d. A highly contagious virus emerges that turns humans into zombies

e. The Federal Reserve Bank lowers U.S. interest rates

a and e

b and c

a, d, and e

c and d

e only

all of them