Trench warfare caused the immobilization of troops on the

western front.
middle eastern desert.
eastern front.
mountains in russia.

Trench warfare caused the immobilization of troops on the: a. western front.
trench warfare is a land warefare using for fighting lines, which is the troops are protected and substantially sheltered from artilery.

hope this help

Sonar is an application of the doppler effect used by submarines.  this test was on k12.