During world war ii, the effectiveness of german u-boats and underwater mines was ended by the development of select one: a. acoustic countermeasures. b. sonar. c. centimetric radar. d. both sonar and centimetric radar. e. all these answers are correct.

richard milhous nixon (january 9, 1913 – april 22, 1994) was the 37th president of the united states, serving from 1969 to 1974, when he became the only president to resign (quit). he is also known for corruption and the watergate scandal which resulted in the public losing trust in him and his resignation.