I think the answer is covalent bonds.
https://mgdic.files.wordpress.com/2016/12/unit-operations.pdf this
First you need to know what is a semantic memory
Semantic memory, is a more structured record of facts, meanings, concepts and knowledge about the external world that we have acquired.
So ,The element which is a semantic memory is learning from her father that salt water is more dense than fresh water.
Hope this helped :)
