Which Statement Best Characterizes War on the Western and Eastern

Which statement best characterizes war on the western and eastern fronts?

A) The western front was marked by trench warfare and immobilization while the eastern front was more mobile.
B) Both fronts were mired in trench warfare that kept both sides immobilized.
C) Both sides were marked by mobility as a result of modern warfare techniques.
D) The eastern front was marked by trench warfare and immobilization while the western front was more mobile.
E) The western front's trench warfare led to an enormous loss of life while the mobility of the east caused less death.