can someone explain B a bit more? confused by JY's explanation

AC D says people are "generally" not indifferent. This wording through me off as when you negate to destroy it becomes generally indifferent. If people are indifferent only in the general sense (like not all cases), how does that still destroy the argument?

When I drill with the new website and finish I do not see an option to blind review? Every time I click finish it just shows my score.