Which of the following is a key feature of a non$-$relational database like NoSQL?

a$.)$

It efficiently uses indexes as a means to provide efficient access to data and is supported directly in the database rather than maintained in the application code.

b$.)$

It uses expressive query languages to be able to access and modify the data.

c$.)$

It ensures strong consistency such that applications should be able to read what has been written to the database immediately.

d$.)$

Flexible data models allow for easy storage to combine data of any structure and dynamic changes to the schema.