Quick tip for anyone struggling to find the sufficient and necessary conditions in examples that begin with an indicator (#2, 3, 5). Rewrite the question with the word "cannot."

Ex: No birds are trees.---> Birds CANNOT be trees. Then, the lawgic translation is B--> /T.

It works with the other examples as well: No holiday falls within the month of August= Holidays CANNOT fall within the month of August. (H--> /A) OR

August CANNOT have holidays. (A--> /H).

This worked much more intuitively for me than just figuring it out by myself. I guess you could also say that the negated necessary term will always be the second premise as well...Whatever works lol!

You're putting two separate concepts together. The sufficient condition is the unscheduled stop, the necessary condition is the safety demand. The ship will only stop for the safety demand. If the ship makes an unscheduled stop then that is ONLY because there was a safety demand. If the ship stops for a safety demand that does not mean that it was unscheduled. For example, if the ship stopped on a scheduled refill for fuel, that is both scheduled and for safety.