What was a major invention that caused massive casualties during the war?

Trench warfare The hand grenade, long used in crude form, developed rapidly as an aid in attacking trenches. Probably the most important was the introduction of high explosive shells, which dramatically increased the legality of artillery over the 19th-century equivalents.

Explanation:

3.a

4.d

5.b

6.b

7.c

8.a

9.d

10.a