Our teacher set us such a difficult math problem _we couldn't work out.A.as b.that这到底是as引导的定语从句,还是such.that结构?

Our math teacher is s(?) with us. our teacher's funny stories made us (feel)happy It's time that we set about doing our homework.改写:It's time for us to do our homework. We all love our English teacher.She's always f________to us. We are ( s )our teacher gives us good (a ).填单词,首字母已出 Our teacher tell us to ___ (do something very often to improve one's skills)our ...Our teacher tell us to ___ (do something very often to improve one's skills)our spoken English every day. Our teacher told us ______in the hallways. our teacher is---------------------(help)to us Our English teacher often tells us j_____. Our teacher often talks us English Our teacher takes us to ___ ___. our teacher often （say ）us stories Our teacher teaches us maths.同义句 Our teacher is very -----(friend) to us. These day our teacher teaches us English____ Our teacher tell us plants d____from seeds. Last week our maths teacher set so difficult an examination problem___ none of us worked out.A.thatB.whichC.as D.so that.Please explain. our teacher set us such a difficult maths problem we couldn't workd outA.that B.as C.which D.even