UML use case diagram 2 actors connected with 1 use case

Question

What this example shows?

Does it mean:

a) Actor1 and Actor2 can use Use Case1
b) both Actor1 and Actor2 are needed to start Use Case1 (for example two people need to turn keys for firing rocket?)
c) Actor1 can start Use Case1 and Actor2 does something later
d) Actor2 can start Use Case1 and Actor1 does something later

Am I right that answer B is correct and:

A would be:

C would be:

D would be:

Answer 1

Your response A i.e. Actor1 and Actor2 can use UseCase1 is the correct one.

Of course you can model that with your second diagram but in this case the model is a little bit different. Actor1 and Actor2 can also use UseCase1 but this is due to the fact that they are specialization of Actor3 which is the only kind of actor having acces to the usecase1