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【简答题】
以下各个关于圆锥曲线的命题中 ①设定点F 1 （0，-3），F 2 （0，3），动点P（x，y）满足条件|PF 1 |+|PF 2 |=a（a＞0），则动点P的轨迹是椭圆或线段； ②过点（0，1）作直线，使它与抛物线y 2 =4x仅有一个公共点，这样的直线有3条； ③离心率为 1 2 ，长轴长为8的椭圆标准方程为 x 2 16 + y 2 12 =1 ； ④若3＜k＜4，则二次曲线 x 2 4-k + y 2 3-k =1 的焦点坐标是（±1，0）． 其中真命题的序号为______（写出所有真命题的序号）
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皮皮学刷刷变学霸
举一反三
【单选题】——_____. ——You did? That's great! Congratulations.
A.
My wife had a baby last night.
B.
Today is my birthday.
C.
I just got a pay rise.
D.
I failed in my driver's test.
【简答题】在单处理机环境下的多道程序设计具有多道、( 1 )和( 2 )的特点。
【单选题】I apologize for over-speeding, but my wife a baby and I had to rush her to the hospital.
A.
is having
B.
was having
C.
promoted
D.
motivated
【单选题】My wife had a good reason to be angry with me. I to her in the first place.
A.
shouldn’t have lied
B.
shouldn’t lied
C.
had lied
D.
mustn’t lie
【单选题】具有凝集红细胞特性，主要导致禽类感染，也能引起哺乳动物感染的病原是（ ）
A.
高致病性禽流感病毒
B.
兔出血症病毒
C.
新城疫病毒
D.
猪细小病毒
E.
猪瘟病毒
【简答题】I had offered to watch my 3yearold daughter, so that my wife could go out with a friend.I was getting some work done in my study while she ____ to be having a good time in the other room.No problem,...
【单选题】My wife was still worried because ______.
A.
it was going to rain
B.
we had a large garden
C.
it was hard to feed so many people
D.
Aunt Clara had a sweet voice
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