Hey there,
It honestly depends on what universities you're aiming for. Psychology is regarded as a soft subject, hence I would recommend option (B) if you're aiming for Oxbridge or a top Russel Brown University. However, if you really despise chemistry, then its better to pick Option (A) as its always better to do something you're passionate about, rather than suffering for 2 years.
Choose the subjects that YOU think that you'd enjoy and that you're inclined to, as you'll be able to achieve higher grades for that. On a side note, you could always do Maths (if u enjoy it) as its a safe option.