The type of figurative language is idiom
In an attempt to keep her plants from freezing, she left the stove on to keep them warm.
The first-aider will be ready with a first aid kit and will be on guard in case of accidents or injuries. First aid means, the first action done on someone who is injured or not feeling well within the designated place. He/she must know some first aid treatments or methods, such as treating a cut or bruise, giving artificial ventilation and CPR, etc.
I think the correct answer would be D. It makes the most sense to me!
