d) Natural language :

Natural language Interfaces are designed for understands human speech and to give prompts and responses in natural language.

This should be the easiest type of interface for any of us to use and shouldn’t require too much training.

However, it has some problems where :
the processing is quite intensive and this can make the software slow, Regional accents means that many people say the same words in very different ways, People use different phrases to mean the same thing, so it’s hard for the software to understand everything and also People often don’t like the sound of computerized speech.