K12
The word 'countdown' — as in '3, 2, 1, liftoff' — was popularized by a specific source before real rocket launches adopted it. Where did NASA and the space community actually borrow the countdown concept from?
A
A 1929 German silent film about a rocket launch
B
World War II artillery firing procedures
C
A 1950s sci-fi radio drama called 'X Minus One'
D
Early Soviet missile test protocols
E
A Jules Verne novel from the 1860s
