1. Going by the meaning of the term '<em>northernmost'</em>, which is a location that is situated furthest to the north, we can conclude that North Korea is the country that shares a border with the northernmost part of China.
2. China and Mongolia are among the several countries found between the 105° E and 135° E lines of longitude.
the world's current population is 7.3 billion and the world population in 1915 was 1.8 billion. The increase over the past century is 7.3 billion - 1.8 billion = 5.5 billion. So, the correct answer would be "more than 5 billion" (option D).
