I think it is at least AIT HAS TO BE at least
The correct answer is option b) "frictional". Frictional unemployment occurs when someone quit his job before finding a new one. In this case Joe is experiencing tireness and he needs to take a break of his current work. This type of unemployment is natural and could be considered beneficial since people look for other jobs where they could be more productive.
because they dominated The delian League
B. the rudder
this is because they made advancements in irrigation and water control