Which of the following phrases from mandela’s speech is an example of a metaphor?

“the children, the greatest of our treasures”
“the children must play in the open field”
“the relentless pursuit of the purposes”
“no longer tortured by the pangs of hunger”

I believe that the phrase from Mandela's speech that is an example of a metaphor is the first one - 'the children, [...] the greatest of our treasures."
A metaphor is a type of comparison, where two or more things are compared without using words such as like or as. Here, the children are the greatest of our treasures - they are compared to a treasure, something which is the most important thing of all.