Could be true. We know that all popular novelists can vividly imagine large numbers of characters, but it is possible that some novelists who are not popular can also do this. A necessary condition can be satisfied without the sufficient condition being true.

Could be true. We know that all popular novelists are capable of empathizing with people whose goals are different, but this implies that if a novelist cannot empathize in this way, then they are not popular. So, some unpopular novelists might exist who lack the ability to empathize.

Must be false. If an author is a popular novelist, then that novelist must have the ability to empathize with those who have completely different goals. So it's impossible for some popular novelists to be incapable of empathizing with those who have different goals.

Could be true. We know all people capable of empathizing with those who have completely different goals have doubts about the value of their own desires. It is also possible that all people who have doubts about the value of their own desires are capable of empathizing. (If we know that all As are B, it's possible that all Bs are A.)

Could be true. We know that all popular novelists have doubts about the value of their own desires. It is also possible that most writers who have these doubts are popular novelists. (If we know that All As are B, it is possible that most Bs are A.)