置火中易燃烧发生爆鸣声且有闪光，无灰渣残留的药材是（）
A.海金沙
B.儿茶
C.五倍子
D.冰片
E.芦荟
参考答案：A
— It's dangerous to swim here. Look at the sign.
— Oh, I ______ notice it. Thanks for telling me. [ ]
A. haven't
B. won't
C. don't
D. didn't
如图所示，电路两端电压U保持不变。
(1)若电阻R1、R2、R3消耗的电功率一样大，则电阻之比R1:R2:R3=____；
(2)若电阻R1=R2=R3，则它们在相同时间内产生的热量之比Q1:Q2:Q3=____。
