An adjective clause functions as an adjective, that is, it gives some information about a noun in a sentence (or a pronoun) ( information which is not an action).
The noun modified here is "knife" and the information about the knife, that is the complete adjective clause is "<span> that his dad gave him.
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Here you go.
Much to Bradfords astonishment, Samoset addressed the Pilgrims in broken English. Samoset persuaded his kindred Indians' to restore the pioneer's apparatuses. He influenced Massasoit to offer his regards to the Pilgrims and acquainted them with one of his friend's, Squanto.
