22. The first thermionic valve was invented by
A. Thomas Edison
B. Richardson
C. J.A. Fleming
D. Lee De Forest

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23.  Gunpowder was invented by
A. Roger Bacon
B. Colt
C. C.V. Raman
D. Dr. Gatting

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24.  For which invention is Otto Hahn famous?
A. Atom bomb
B. Television
C. X-rays
D. Miner's safety lamp

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25.  Leprosy bacillus was invented by
A. Koch
B. Hansen
C. Fleming
D. Harvey

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26.  X-rays were discovered by
A. Becquerel
B. Roentgen
C. Marie Curie
D. Van Lue

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27.  Who discovered cement?
A. Agassit
B. Albertus Magnus
C. Joseph Aspdin
D. Janseen

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28.  Who discovered North Pole ?
A. Amundson
B. Robert Peary
C. John Cobot
D. Captain Cook

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