Concentrate on your PMR first , then think later . It really depends on your interest and capability .

Both are considered above average subjects , meaning you'll have to work hard for either of these subjects . I'm taking Biology , it requires reasoning , reading and retaining the facts that you've read and applying it during exams . It's interesting too . Not too sure about LK as it isn't one of my subjects but it is very hard to score . Nobody got A+ for it in 2010 . But if you have good teachers [ examiners / experienced ones ] and is really willing to learn then you're good to go . It's not that you will be good in it if you like drawing , it's different . You'll have to visualise objects in 3-dimensions and draw plans . Your eyesight must be good too .