The correct answer is B) a deadly virus emerges that can pass from human to human.
The issue that can affect the human population is a deadly virus emerges that can pass from human to human.
Scientists and governments are concerned with the spread of viruses because they put at risk human lives. A virus can spread very fast from one region to another, putting many lives at risk. Let's just remind of the case of the black death in Europe that killed millions of people and devastated that part of the world. The Great Plague killed almost 200 millions of people between 1347 and 1351.