Which group best describes the order of events in the development of the airplane?

group a

hot-air balloon flights pioneer air travel

aviators fly gliders—heavier-than-air aircraft with no engines

development of engine-powered machines with propellers and lightweight motors

first-ever flight across the english channel

construction of the first military airplanes

world's first scheduled commercial airline

group b

development of engine-powered machines with propellers and lightweight motors

world's first scheduled commercial airline

first-ever flight across the english channel

hot-air balloon flights pioneer air travel

aviators fly gliders—heavier-than-air aircraft with no engines

construction of the first military airplanes

group a, or group b?