面点制品的温度低至（）℃时，其中的淀粉老化速度加快。
A. 1~3
B. 2~5
C. 3~7
D. 4~8
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蜗杆传动用于传递空间交错两轴间的运动和转矩，通常两轴间的交错角等于（）
A. 180度
B. 90度
C. 45度
D. 30度
You want to display the titles of books that meet these criteria: 1. Purchased before January 21, 2001 2. Price is less then $500 or greater than $900 You want to sort the results by their data of purchase, starting with the most recently bought book. Which statement should you use? （）
A. SELECT book_title FROM books WHERE price between 500 and 900 AND purchase_date < '21-JAN-2001' ORDER BY purchase_date;
B. SELECT book_title FROM books WHERE price IN (500,900) AND purchase_date < '21-JAN-2001' ORDER BY purchase date ASC;
C. SELECT book_title FROM books WHERE price < 500 or > 900 AND purchase_date < '21-JAN-2001' ORDER BY purchase date DESC;
D. SELECT book_title FROM books WHERE (price < 500 OR price > 900) AND purchase_date < '21-JAN-2001' ORDER BY purchase date DESC
将土壤矿质颗粒分为物理性沙粒和物理性黏粒的科学家是（）
A. 美国人
B. 中国人
C. 德国人
D. 前苏联人
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