The two verbal extensions that increase the valency of the verb are:
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Causative - This extension allows the subject to cause someone else to perform the action of the verb, thereby adding an additional participant to the event.
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Applicative - This extension adds an object or participant to the verb that is not typically included in the intransitive or transitive form of the verb, effectively increasing the valency by introducing a new argument.
The other options (Reciprocal, Passive, and Neuter) do not increase the valency of the verb.