When TedX speaker Julia Middleton talks about core and flex with respect to cultural intelligence, what is she referring to$?$

Question $3$ options:

Core refers to your level of cultural intelligence at a subconscious level.

Core refers to your core strength.

Flex refers to your ability to change your behaviours, values, beliefs to gain trust with others. Core refers to behaviours, values, beliefs you're unwilling to flex on$.$

Flex refers to your ability to go with the flow while travelling. Core refers to your ability to stay strong and level$-$headed while travelling.