Final answer:
One potential problem with the use of modern weapons in WWI was the high casualties they caused due to their devastating firepower, such as machine guns, long-range artillery guns, and airplanes.
Step-by-step explanation:
One of the potential problems with the use of modern weapons, such as machine guns, modern howitzers, and airplanes, on the battlefields of Europe during World War I was the devastating casualties they caused. The introduction of machine guns, which could fire hundreds of rounds per minute, made infantry attacks extremely dangerous, turning soldiers into easy targets. Additionally, long-range artillery guns and airplanes allowed for massive bombings and shelling, leading to widespread destruction and loss of life.