I dont understand when to know to take the contrapositive. When I tried the question myself I chose /HWA as the sufficient already, and thus did not need to take the contrapositive. How would I know to do that or take the contrapositive?

@GraceArciniega Which textbook were you using? And whcih did you find to end up being more beneficial? This or textbook? Thanks

I dont understand how if people are 'less objective' regarding matters which they possess extensive knowledge on rather than ones they do not, how would that mean that they are not objective about either? Wouldn't this imply that they are at least a little bit objective about at least the subject which they do not possess extensive knowledge? Thanks.