The game tells us that "a crew of UP TO five workers" is "selected from the following list" of seven workers. This means that not all of the seven workers can be selected to be part of the crew. However, each worker that is selected as a crew member must do at least one of the five tasks, as Rule #3 states. This allows us to have a crew of four members, as (B) shows.
Does that make sense? Please let us know if you have any other questions and best of luck with your studies!
