The causal factor is simply that the two events or states referred to are mutually exclusive: if one occurs, then the other will not. The two alternatives have equal natural prominence.
Alternation is a non-chronlogical addition type where either one or the other of the propositions applies. There is no time element, and one does not support the other, a choice must be made between the two.
Some languages achieve this by simple juxtaposition.
Alternation in Kovol makes use of interrogative clauses juxtaposed, usually with the o particle between them.
option 1 ig o option 2 ig o.
There may be times ig or o is implicit.
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Alternation between 2 options has been seen quite regularly in speech and there are simple examples taken from DA.