It is already hot, so it makes it more humid
The correct answer is - intraplate volcanism.
The Hawaiian Islands are volcanic islands, thus islands that have been created by volcanic activity. Unlike most of the volcanic islands, or most of the volcanoes, they are not related to any type of volcanism asociated with plate boundary. These islands are in fact associated with intraplate volcanism.
The intraplate volcanism, unlike the other volcanisms, appears inside the plate, not on the boundary of it. The other, more common name, used for this volcanism is hot spot volcanism. This type of volcanic activity appears on places where there's a hot spot, so even though the plate is on top of it, it manages to penetrate through it, and create volcanoes on the surface.
Elevation and ocean currents
The correct answer Having a shoreline makes shipment by sea possible, which is less expensive than over land
North African and Middle Eastern countries can't join the EU since they're not from Europe, and regarding security, it's all the same now since it's not the middle ages any more.