Question

During world war ii, the effectiveness of german u-boats and underwater mines was ended by the development of select one:

Answer 1

select one:
a. acoustic countermeasures.
b. sonar.
c. centimetric radar.
d. both sonar and centimetric radar.
e. all these answers are correct.
A quick google search said centimetric radar was invented in 1935 during the range of WWII.
Hope I helped some