Does it take more time to be removed from an email list than it used to take? A study of 100 large online retailers revealed the following:

a. Give an example of a simple event.
b. Give an example of a joint event.
c. What is the complement of "Needs three or more clicks to be removed from an email list"?
d. Why is "Needs three or more clicks to be removed from an email list in 2009" a joint event?