Answer:
D
Step-by-step explanation:
He has a heart of gold is a metaphor. A, He is a good person, is not comparing the character to anything. B, Her voice was like a song, is a simile, as it uses the word like. Same for C, Her eyes were like ice. Therefore, D is the only option left: He has a heart of gold. It is comparing the character, or the character's heart, to gold, without using the words like or as.