Which of these events or terrestrial bodies normally cannot be seen more than twice in one's lifetime ? a) Meteor Shower b) Waxing Moon c) Halley's Comet d) Sighting of Ursa Major

Ques: Which of these events or terrestrial bodies normally cannot be seen more than twice in one's lifetime ?
a) Meteor Shower 
b) Waxing Moon
c) Halley's Comet
d) Sighting of Ursa Major

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