设A为4×3阶矩阵，B为3×4阶矩阵，则下列说法正确的是 A: |AB|=0 B: AB不可逆 C: |AB|=|BA| D: BA可逆 E: |BA|=0 F: |BA|≠0

background:url(2、png),url(1、jpg),url(3、png),url(4、jpg);},表示哪张图片处在最上层() A: 2、png B: 1、jpg C: 3、png D: 4、jpg

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求电路中a、b端的等效电容Cab=（ ）F。 [img=252x153]17d604470326e0f.png[/img] A: 2.5 B: 2 C: 4 D: 3

普通话声调音位/51/的音位变体是( ) A: [51] B: [51][53] C: [51][21] D: [53][21]

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设a=1, b=2, c=3, d=4，则表达式：“a＜ba: b＜ba: c＜da: d”的结果为( )。 A: 4 B: 3 C: 2 D: 1

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Given a grammar A→bA|ca, the grammar sentence is( )。 A: bba B: cab C: bca D: cba