Start by determining the population of Paraguay. The bar hits right at the horizontal line for 5 , which is in millions, so there are 5 million people in Paraguay. Now use the definition of population density in the question.
area  population ​=400,0005,000,000​
Be very careful with the number of zeroes you put in the fraction-the answer choices are pairs that vary by a factor of 10 , meaning the test writers expect you to miss a zero. The answer must be greater than 1, since your numerator is bigger than your denominator, so eliminate (A) and (B). Choice (C) also seems too small, but check the math on your calculator (carefully). You should get 12.5 people per square kilometer, so (D) is correct.