三相交流电三个电动势的最大值相等，角频率相同，三者之间的相位差相同，互为（）。
A.90°
B.120°
C.150°
D.180°
参考答案：B
根据首字母提示，填入一个正确的单词形式。
1. You are good at t ______ to people. They all like you.
2. Let me look at you c______. You aren't hot.
3. I hope to have a happy family s______ in the future.
4. I will work hard to i______ English.
5. Slow is the o______ of fast.
预防人群碘缺乏病的最方便而实用的措施是（）
A.在食盐中加入碘化钾或碘酸钾
B.在食用油中加入碘盐
C.消除其他致甲状腺肿的物质
D.净化或更换水源
E.服用含碘药物
