C is the answer , breathing problems and air pollution relate
Here is the answer to the given question above. Based on the given sample sentences, the best way to combine the sentences using a semicolon would be this: <span>The world’s nations must cooperate; one nation cannot solve the world’s problems by itself. The correct answer would be the second option. Hope this helps.</span>
B. The most beautiful moments of Life are brief
<span>Vladimir Lenin became the head of the Russian government after the October </span><span>Revolution of 1917. </span>