what do you mean by negligible compressibility ?

To understand negligible compressibility, we need to understand the meanings of the words that make up this word-

Negligible : Not significant or important  enough to be worth considering

Compressibility :  it is the ability of an object to be compressed.

Thus, negligible compressibility means that the object does have the ability to compress but the compression is not significant enough to be considered

Nice Answer Drishti!  

And Ya , it is the correct answers 
some examples are iron copper etc.