Question

complete the sentence with the best relative pronoun. the term iceberg describes an enormous floating mass of ice has broken off a glacier.

Explanation:

We need a relative pronoun to introduce the relative clause that modifies "an enormous floating mass of ice". The relative pronoun should act as the subject of the verb "has broken". Since the antecedent is a thing (the mass of ice), the appropriate relative pronoun is "that" or "which". In defining relative clauses (where the clause is essential to identify the noun), "that" is often preferred, especially when the noun is a thing. So "that" fits here.

Answer:

that