DHA的数字命名法
A. 18:3（6c，9c，12c）
B. 18:2(9c,12c)
C. 22:6(4c,7c,10c,13c,16c,19c)
D. 20:4(5c，8c，11c，14c)
纯净的油脂是什么颜色
A. 109°28′
B. 108°25′
C. 104.5°
D. 109°25′
水分子的四面体结构中两个O-H键间的夹角为
A. 109°28′
B. 108°25′
C. 104.5°
D. 109°25′
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A. He was ordered to clear the apartment by his mother last time.
B. He has not cleared the apartment since his mother's visit.
C. He has cleared the apartment several times since his mother's visiting.
D. He asked his mother to clear the apartment last time.
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