1. Stating the problem: Seawater contains 1.75 grams of salt per 500 milliliters of water. We need to find how many grams of salt are present in 2 liters (2000 milliliters) of seawater. 2. Convert 2 liters to milliliters to match the units: $$2\text{ liters} = 2000\text{ milliliters}$$. 3. Find out how many 500 ml portions are in 2000 ml: $$\frac{2000}{500} = 4$$. 4. Since each 500 ml contains 1.75 g of salt, multiply this by 4 to find the total salt in 2000 ml: $$1.75 \times 4 = 7$$ grams. 5. Final answer: There are 7 grams of salt in 2 liters of seawater. Therefore, the correct choice is b. 7 g.