In the sentence Your heating costs can be reduced with insulation, the word be is a __ a. linking verb b. principal verb C. preposition d. helping verb

In the sentence "Your heating costs can be reduced with insulation," the word "be" is a:d. helping verbThe word "be" is used here as part of the passive voice construction "can be reduced," where "can" is a modal auxiliary verb and "be" helps form the passive voice with the past participle "reduced."