设方阵\( A \)和\( B \) 等价，\( A \) 的所有\( k \) 阶子式全为零，则( ) A: \( r\left( B \right) < k \) B: \( r\left( B \right) = k \) C: \( r\left( B \right) \ge k \) D: \( r\left( B \right) \le k \)

1.设${{J}_{k}}=\int_{{}}^{{}}{\frac{dx}{{{\left[ {{(x+a)}^{2}}+{{b}^{2}} \right]}^{k}}}}\quad (b\ne 0)$，则${{J}_{k}}$满足( )。 A: ${{J}_{k+1}}=\frac{1}{2k{{b}^{2}}}\left[ (x+a){{\left( {{(x+a)}^{2}}+{{b}^{2}} \right)}^{-k}}-(2k-1){{J}_{k}} \right],\quad (k\ge 2)$ B: ${{J}_{k+1}}=\frac{1}{2k{{b}^{2}}}\left[ (x+a){{\left( {{(x+a)}^{2}}+{{b}^{2}} \right)}^{-k}}+(2k-1){{J}_{k}} \right],\quad (k\ge 2)$ C: ${{J}_{k+1}}=\frac{1}{2{{b}^{2}}}\left[ (x+a){{\left( {{(x+a)}^{2}}+{{b}^{2}} \right)}^{-k}}+(2k+1){{J}_{k}} \right],\quad (k\ge 2)$ D: ${{J}_{k+1}}=\frac{1}{2{{b}^{2}}}\left[ (x+a){{\left( {{(x+a)}^{2}}+{{b}^{2}} \right)}^{-k}}+(2k-1){{J}_{k}} \right],\quad (k\ge 2)$

在网页中插入两个id名分别为left和right的<;div>;标签，（）两个元素都右浮动。 A: B: left, C: right{float:left;} D: E: left, F: right{float:right;} G: H: left{float:left;} I: right{float:right;} J: K: left{width:100px;float:left;} L: right{margin-left:100px;}

计算向量场$A = \left( {{x^2} - y} \right)i + 4zj + {x^2}k$的旋度。 A: $4i+ 2xj - k$ B: $ - 4i - 2xj - k$ C: $ 4i +2xj + k$ D: $ - 4i - 2xj + k$

如果\( k = \lim \limits_{x \to \infty } { { f\left( x \right)} \over x},b =\lim \limits_{x \to \infty } \left( {f\left( x \right) - kx} \right) \)，则称\( y = kx +b\)为曲线\( y = f(x) \) 的一条______ 。

In "Left Behind", what is the order the author organized her passage? A: Things left behind→memories left behind→love left behind B: Memories left behind→things left behind→love left behind C: Love left behind→memories left behind→things left behind D: Love left behind→things left behind→memories left behind

My house is __________(on the left / in left side). A: on the left B: in left side

The museum is __________. A: in your left B: in the left C: on your left D: at the left

     说明下列信号是周期信号还是非周期信号,如果是周期信号,试确定其周期。[br][/br]x(k)= e ^{ j ^{\left(\frac{k}{4}- x \right)}}

Eat to your ______,and drink to your_______.? right, left|right, right;|left, left|left, right