is there a discount ( ) last month

is there a discount ( ) last month There is a discount ()last year is cards.a:in,b:on,c:of,d:at discount可数吗?为什么是there is a discount 将这个句子改为同义句THERE IS A DISCOUNT ON LAST'SPOSTCARDSTHEY SELL LA there is a 30% discount 翻译 There is a discount on last year's cards句中为什么用is后接cards There is much_(little)rain this month than last month. discount不可数呀,可课本上却说there is a discount on.,用了a －when------ the school music festival?－Last month.A.is there -----is the second last month of a what is the last month of a there （ ）a lot of rain here last month