Adding onto what
@Stefano said, for T/F/CS questions, you should look for something that
directly affirms or
directly contradicts the statement. Otherwise, the answer is 'cannot say'. You do not rely on any 'general knowledge'.
From my understanding this is what distinguishes T/F/CS from T/Probably True/CS/Probably False/F questions (i.e. 'inference' questions in Watson Glaser), in which you are allowed to use 'general knowledge' to determine whether something is probably true or probably false.
Eg
'Most people who have salmonella experience symptoms of stomach ache and runny stool.'
Statement: 'It is common for people with salmonella to use the bathroom.'
In T/F/CS - cannot say. Nothing in the statement directly confirms or denies the link between salmonella & bathroom use
In T/PT/CS/PF/F - PT, because most people who have stomach ache/runny stool will use the bathroom (general knowledge)
Hope this helps