Which marine resource is too expensive to recover at this time due to the low market value of the resource?
a. Magnesium compounds
b. Manganese nodules
c. Sand and gravel
d. Salt
e. Rare-earth elements
Question 2What is the largest known reservoir of hydrocarbons on Earth?
a. Coal deposits
b. Oil reserves
c. Ethane pools
d. Natural gas
e. Methane hydrate