The prepositional phrases in the sentence<em> In 1647, the first tax-supported schools were established by law in the United States</em> are:
In 1647;
by law;
in the United States.
Explanation:
<u>Prepositional phrases</u> are those phrases that contain a preposition followed by its object -noun, pronoun, clause or gerund- and any other modifier. These phrases can function as an adjective or as an adverb so as to modify another element in the sentece. The phrases that meet these requirements are <em>in 1647</em>,<em> by law</em> and<em> in the United States</em>.