I really don't know which pair to choose.（同义句转换） I really don't konw which pair _ _ choose.

I really don't know which pair to choose.（同义句转换） I really don't konw which pair _ _ choose.
I really don't know which pair to choose.（同义句转换） I really don't konw which pair _ _ choose.

I really don't know which pair to choose.（同义句转换） I really don't konw which pair _ _ choose.
I really don't konw which pair （I）（should）choose.