Answer:
One infinitive.
Explanation:
Verbals are formed from verbs, but they act as a noun, adverb or adjective.
There are three types of verbals: infinitive, gerund, participle.
Gerund acts as a noun, participle acts as an adjective and infinitive can act as a noun, adverb or adjective.
From the previously mentioned verb forms, in this sentence, we can only find an infinitive - to make (to make a promise - infinitive phrase).
