Answer:
They should only drink a tablespoon at a time and at very long intervals because the salinity in the ocean water will only dehydrate them more.
Explanation:
I would go with B but wait for some one else to answer just in case
MORE CAUTIOUS SORRY FOR PUTTING IT IN ALL CAPS BUT
Answer: whether, weather
Explanation: Looking at the Grey sky, Becky wondered WHETHER the WEATHER would ruin the class trip.
Weather and whether although having a similar pronunciation do not perform same function in a sentence.
Weather is used to describe the temperature and precipitation activity at a certain point in time while WHETHER is a word used as a condition between two likely outcomes.