(1) As we have seen earlier, a score of 8 is fairly rare, so to score an overall 7, a candidate would need the following scores: ...
Another way to say the second part of the sentence:
If a candidate wanted to score an overall , she would need the following scores. (conditional)
(2) In fact it can be concluded that your speaking score is awarded purely on the basis of your spoken language. In theory it could be possible for a candidate to tell lies and still achieve a high score.
Why the author use 'can' in the first sentence but 'could' in the sencond one? What does this usage imply?
The first one (can) is not arguable. It's fact. The second one (could) is more hypothetical, so it uses a conditional. ==> If a candidate told lies, it could be possible for her to get a high score. or If a candidate told lies, she could get a high score.
Sorry, I realize it's not easy stuff to grasp.
Student or Learner