c# - LINQ joining multiple lists -

i want able join multiple lists. i'm trying reply user best suitable answer. program reads sentence typed in user, stores infinitives, nouns, articles , adverbs in seperate lists , tries find best answer or reply user in list of structs pre-defined answers joining lists.

so list1 (the answer list) looks this

public struct ll {     int index;     string infinitive;     string noun;     string article;     string adverb;     string preposition;     string answer;         } public list <ll> list1; 

with below data:

when example user inputs sentence "what can find" join script should return 2 possible answers, being "i can find information" , "what want me find", because infinitive can found in users input , no noun, article, adverb, etc.

but when sentence more explicit "what can find here", return "i can find information", search done on infinitive in combination adverb.

also when user asks: "what know hobbit" return nothing combination "know" , "this" unknown, "what know hobbit" return "this know about"

i'm trying accomplish linq join statement like

var query = x in answer             join y1 in infinitive on x.infinitive equals y1             join y2 in noun on x.noun equals y2             join y3 in adverb on x.adverb equals y3             etc...             select x.index; 

the problem in case user types in "what know hobbit" return nothing because it's trying match user's infinitive "know" in combination preposition "about", should answer "this know about".