(a) ten percent of discount

Dear native English speakers,
Which one would be used?
(a) They gave me ten percent discount.
(b) They gave me a ten percent discount.
(c) They gave me ten percent of discount.
(d) They gave me a ten percent of discount.
(e) They gave me ten percents discount.
(f) They gave me ten percents of discount.

I guess (b) would be fine.

Thanks in advance.

Hirashin from Kyoto, Japan

Only B works. I would note that it's far more usual to write "percent" as "%" (alongside a numeral, so in this case "10%"), though this is not essential.

A doesn't work because "ten percent" is just a modifier for "discount"; it's wrong for the same reason "They gave me discount" is wrong. An article is needed.

C and D don't work because while "percent" can be used with "of", they way you're doing it here causes "discount" to not have an article. In D, the article gets applied to "10%", which in most contexts makes no sense. You could fix C by putting "the" right before "discount":

"They gave me 10% of the discount."

But that means something totally different; if we're talking about a 10% discount, that would mean that you got 10% of that 10% discount, i.e. a 1% discount.

E and F don't work because you can't pluralize "percent"; it's a mass noun. This is also why applying articles to "ten percent" makes no sense.

Just a bit of a correction: the last paragraph in my previous post is wrong. "Percents" is not valid in my dialect, but that's because the plural form is also "percent", and a dictionary tells me that this isn't universal. But E and F are still wrong for the same reasons as A and C, respectively.

Yes, only B

Thank you for your help, Julimaruchan and nahadef.