Answer:
B: to support.
Explanation:
The phrase "to champion" is used to refer to something that is given support, protected or given a chance. It is a verbal phrase that is used to refer to any support or chance given.
As stated in the given sentence, the right to be happy is supported by many modern societies. This means that many modern societies believe and put their support for an individual's right to happiness.
Thus, the word "champion" used in the sentence means "to support".
