Formal and respectful tone
The dangers that scientists face when they study volcanoes is the danger of being killed by the hot lava if it erupts so they put their life at risk by studying these dangerous natural disaster.
Both A and D are really close though.I'm leaning more toward D, since it mentions more about getting in the way of the German troops.
Example 1: "There, she helped to set up more resistance groups and organize sabotage actions."
<span>Example 2: "Her actions, along with those of her colleagues, often delayed the arrival of German reinforcements to the front lines of battle."</span>
