"Ezek az amerikai repülőgépek folyóról vagy tengerről szállnak fel?"

Translation: Are these American airplanes taking off from a river or from a sea?

[TakizawaHideaki]

the hint suggests flying not taking off

[RyagonIV]

Well, felszáll means to "fly up", but you don't say that in these circumstances. °-°

[Richard604037]

"Do these American aeroplanes take off from the river or from the sea" wasn't accepted. I appreciate that "a" doesn't appear before river or sea but neither does "egy." Reverting to English, "the" seems to make more sense if we're referring to what the aeroplanes generally do but is it the case that, without "a" it cannot be the river or the sea and must be a river or a sea?

[RyagonIV]

In Hungarian, the egy is optional but the a isn't. If you don't have an a, the noun won't be definite.

[Richard604037]

Thank you. That's an important distinction and I now understand.