Write the next sentence in this paragraph:

How to stay healthy on a cruise vacation
Get vaccinated.
Before departure, make sure you have received all proper medical vaccinations to stay healthy onboard the ship and at ports-of-call. There are many infectious diseases and illnesses that can spread while onboard the ship or in foreign ports.

Pick your answer from:
(a). Even those with low immunity can transmit disease on board to other passengers. Get the vaccination (it's advisable) within 72 hours of arriving in port.;
(b). This involves not only fast-loading, but also extremely dirty decks and cabins. Advise friends and family to get vaccinated before leaving.;
(c). Make sure you are up-to-date on all required or recommended vaccines in your home country. In addition, contact the cruise line and health organizations such as the u.s.;
(d). Make sure you are at least as safe on cruise ships as you are on land. There are also different customs and tariff restrictions.;
(c).