Amazon calculates a product’s star ratings based on a machine learned model instead of a raw data average. The model takes into account factors including the age of a rating, whether the ratings are from verified purchasers, and factors that establish reviewer trustworthiness.
Book seems well done with rigorous language. Beware there is a discrepancy in the first conversation. What the speaker says and what we expect to hear do not match exactly in the 3rd utterance of the speaker. I have not looked at the rest closely, but it does look like a solid preparation is possible. Good luck to all test takers in May! Bonne chance à tous!