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【单选题】
某中药水体液中,在进行 HCl-Mg反应时,加入Mg粉无颜色变化,加入浓HCl则有颜色变化,只加浓HCl不加Mg粉也有红色出现,加水稀释后红色也不褪去,则该提取液中可确定含有( )A.
异黄酮
B.
黄酮醇
C.
花色素
D.
黄酮
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举一反三
【单选题】He enjoyed living in the small town at first but the _______ soon wore off, and he began to miss city life.
A.
certainty
B.
productivity
C.
novelty
D.
morality
【简答题】已知函数f（x）=ax 3 +bx 2 +（b-a）x（a，b是不同时为零的常数），其导函数为f'（x）． （1）当 a= 1 3 时，若不等式 f′(x)＞- 1 3 对任意x∈R恒成立，求b的取值范围； （2）若函数f（x）为奇函数，且在x=1处的切线垂直于直线x+2y-3=0，关于x的方程 f(x)=- 1 4 t 在[-1，t]（t＞-1）上有且只有一个实数根，求实数t的取值范围．
【简答题】He wasn’t sick. He wasn’t old. And he wasn’t losing. He had a very good final season and won his last in 2008. And then he walked away. Lloyd Carr was 62. That’s a few years earlier than retireme...
【简答题】函数y=f（x）在区间（0，+∞）内可导．导函数f ′ （x）是减函数，且f ′ （x）＞0，x 0 ∈（0，+∞）．g（x）=kx+m是y=f（x）在点（x 0 ，f（x 0 ））处的切线方程． （1）用x 0 ，f（x 0 ），f ′ （x 0 ）表示m； （2）证明：当x∈（0，+∞）时，g（x）≥f（x）； （3）若关于x的不等式 x 2 +1≥ax+b≥ 3 2 x 2 3 在（0，+∞...
【单选题】Why didn't the fisherman notice the boat began to sink?
A.
He was thinking of money and was too happy.
B.
He was very tired.
C.
He went on pulling the hooks.
【简答题】阅读理解。 He wasn't sick. He wasn't old. And he wasn't losing. He had a very good final season and won his last in 2008. And then he walked away. Lloyd Carr was 62. That's a few years earlier than re...
【简答题】已知函数f（x）=x 3 +bx 2 +cx，其导函数y=f′（x）的图象经过点（1，0），（2，0），如图所示．则下列说法中不正确的编号是______．（写出所有不正确说法的编号） （1）当x= 3 2 时函数取得极小值； （2）f（x）有两个极值点； （3）c=6； （4）当x=1时函数取得极大值．
【单选题】Since he began work, he hasn't ______ asked his father for money.
A.
badly
B.
ever
C.
greatly
D.
very much
【单选题】He began to season the arid ______ in the Middle East.
A.
weather
B.
day
C.
conditon
D.
climate
【单选题】直到舞会开始他才出现。
A.
He didn’t appear until the dancing party began.
B.
He appeared until the dancing party began.
C.
He appeared, but the dancing party didn’t begin.
D.
He didn’t appear, but the dancing party began.
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