types and type

[Jessica725]

Hi there,
I have some confusion about using types and type in the following sentences.
1. What types of smart transport is this book about ?
2. What type of smart transport is this book about?
Which one is correct?I would appreciate your explanation.

 

[probus]

They are both grammatically correct. If you think or want to suggest that there is more than one such type, use the plural version. If there is exactly one, use the singular.

 

[tedmc]

It could be a hybrid, a mix of types.