Why is salt water important to life on earth?

What is the speed of sound in water

Which of the following statements is true? a. there is not enough food produced in the world to feed everyone. b. the biggest cause of hunger and malnutrition is the cost of getting food to people who need it most. c. most countries have enough arable land and resources to feed their own population and export a surplus d. malnourishment is only seen in a few countries with very limited food supplies.

How would i answer this for an exam?