In the early 1900s, what trend emerged concerning chemical weapons? Chemical weapons became deadly, as did other aspects of warfare.
Chemical weapons disappeared and were replaced with less harmful weapons.
Chemical weapons became ineffective as technological advances slowed.
Chemical weapons remained in the form in which they were first introduced.

Chemical weapons became deadly, as did other aspects of warfare.

Explanation:

The knowledge about the affects and impact of chemical weapons was always known to people for a long time. However, it gained more concern only during the early 1900s after the Germans used first large-scale use of chemical at Ypres, Belgium in 1915.

The world has seen its damage and affects for the first time in real warfare and it truly gave a thrilling experience to the people around the world. People started to believe that modern weaponary and chemical weapons could have devastating affects and consequences. Thus, the trend 'Chemical weapons became deadly, as did other aspects of warfare' emerged concerning chemical weapons during the early 1900s.

racism and segregation.