Michael jackson is 50 years old when he was 50 years old when he passed michael jackson was 50

He would be 61 today...

Explanation:

Today, he would have been 61 years old. Last year, his family, friends and fans celebrated his 60th birthday in Las Vegas and Paris and Prince accepted the Legacy Award for Humanitarian Service from the Elizabeth Taylor AIDS Foundation on behalf of their late father.

Your answer would be a participle phrase. That is the only one of the four that functions only as an adjective. Gerund phrases, pronoun phrases, and infinitive phrases all act as nouns. A participle is a verbal ending like -ing or -ed, etc. and a participle phrase adds other words to describe the verb.
Ex: Sally was running to catch the bus. The participle would be running, and the participle phrase would be "running" along with "to catch the bus", for that is describing what she is running for.