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11. The function of a moderator in a nuclear reactor is to
(A). moderate the number of secondary neutrons
(B). moderate the velocity of secondary neutrons
(C). increase the number of fissionable nuclei
(D). control the fission reaction

12. Which planets do not have satellites revolving around them?
(A). Mars and Venus
(B). Mercury and Venus
(C). Mars and Mercury
(D). Neptune and Pluto

13. The absolute zero of temperature is
(A). the starting point of any scale of temperature
(B). the lowest temperature that is theoretically possible
(C). the temperature at which the vapours of all liquid substances freeze
(D). the temperature at which all substances exists in the vapour phase

14. Heavy water
(A). contains more dissolved air
(B). contains more dissolved minerals and salts
(C). contains deuterium in place of hydrogen
(D). contains organic impurities

15. Animal charcoal is obtained by
(A). the destructive distillation of bones
(B). burning the bones of animals in contact with air
(C). burning the flesh of animals
(D). burning the bones of animals out of contact with air