Using kind of

[piggy386]

I have questions regarding the use of "kind of."
I've read on englishplus website that when using kind of always use a singular object of the preposition of. If the object is plural, then use kinds of.

Examples: What kind of salad is this?
(Kind and salad are both singular.)

However, when I browsed eslgold.com, one of the examples showed "What kind of seats does it have?"

I'm bewildered that should the example use "kinds of" in this case according to the rule?

Please advise and explain further the proper use of "kind of".
Thanks very much.

[Tdol]

There are many kinds of seats, but the example used is asking about one kind, though there are many seats. An airplane, for example, has many seats, but they are all the same, so the question is correct.

[piggy386]

Originally Posted by tdol

There are many kinds of seats, but the example used is asking about one kind, though there are many seats. An airplane, for example, has many seats, but they are all the same, so the question is correct.

Thanks for the reply.
Hmm...the rule is not set in stone.
So, whether using "kinds of" or not, it depends on the situation, not only if the object is pural.

[Tdol]

It depends on whether the types are plural not the examples.