Read this sentence: To save the whales became her obsession. Identify what 'to save' is and how it is being used.
-To save' is a gerund and it is functioning as the subject of the sentence.
-'To save' is a gerund and it is being used as the subject complement of the sentence.
-'To save' is a present participle and it is functioning as the subject of the sentence.
-'To save' is an infinitive and it is being used as the subject of the sentence.
-'To save' is an infinitive and it is being used as an adjective in the sentence.