Question

complete the sentence with the best relative pronoun. the invasion of asian toads threatens madagascars unique ecology, is vulnerable to outside predators and diseases.

Explanation:

In this sentence, we are dealing with a non - restrictive relative clause. The antecedent is "Madagascar's unique ecology". A non - restrictive relative clause is separated by commas and gives additional information. When the antecedent is a thing (here, "ecology" is a thing), and we have a non - restrictive relative clause, the relative pronoun "which" is used. "That" is not used in non - restrictive relative clauses. "Who" is used for people. "Whose" is used to show possession.

Answer:

which