2Roy Wilkins was among the last of a generation of civil rights activists who led the nation through decades of change so profound many young Americans are not able to imagine, even less to remember, what segregation was like.
(A) so profound many young Americans are not able to imagine, even less to remember
(B) so profound that many young Americans cannot imagine, much less remember
(C) so profound many young Americans cannot imagine nor even less remember
(D) of such profundity many young Americans cannot imagine, even less can they remember（B）
(E) of such profundity that many young Americans are not able to imagine, much less to remember
OG说，in E， the to in to remember is unnecessary.
why？？
thanks
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