Question

when I last visited Lucknow , I remember clearly that there _____be a house here
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Answer 1

Was

$\bold\red{ Happy \: learning \: ✌. }$

Answer 2

When I last visited Lucknow , I remember clearly that there must be a house here.

Explanation:

• Must is the word which refers to compulsion.
• In the sentence the word "clearly" is used. So the person says that definitely there was a house there, when he visited that place last time.  
• Hence must is used here to show that he is not saying by partial memory ,He remembered it with complete memory when he visited that place last time.