22. The first thermionic valve was invented by
A. Thomas Edison
B. Richardson
C. J.A. Fleming
D. Lee De Forest
23. Gunpowder was invented by
A. Roger Bacon
B. Colt
C. C.V. Raman
D. Dr. Gatting
24. For which invention is Otto Hahn famous?
A. Atom bomb
B. Television
C. X-rays
D. Miner's safety lamp
25. Leprosy bacillus was invented by
A. Koch
B. Hansen
C. Fleming
D. Harvey
26. X-rays were discovered by
A. Becquerel
B. Roentgen
C. Marie Curie
D. Van Lue
27. Who discovered cement?
A. Agassit
B. Albertus Magnus
C. Joseph Aspdin
D. Janseen
28. Who discovered North Pole ?
A. Amundson
B. Robert Peary
C. John Cobot
D. Captain Cook
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