So they're optional, but they're very, very, very highly encouraged that you do these, because this is going to give you practice for the types of problems that are going to be on the exam.
虽然它们是选做的,但是它们非常非常,非常值得你们去做,因为这对你们来说是一次训练,是用来熟悉考试题型的。
So it's something that is openly encouraged to do that.
所以,这是国家广泛地鼓励大家去做的事情。
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