以下是中国四大银行（工、农、中、建）标志，其中仅是轴对称图形，但不是中心对称图形的是（　　）

Look! The     is tall. The     is short.（）

    My name is Lisa. I'm from America, but now my dad, my mum and I are in Shanghai. My dad and my mom are English teachers. But sometimes My father goes to learn Chinese. So he is a student, too. We are in No.12 Middle School.

    Mary, Liu Ying, Wang Haobin are my friends. Mary is from England and she is thirteen years old. Liu Ying is from the capital of China. She and I are fourteen years old. Her English name is Rose. Wang Haobin is from Wenzhou. But he likes Shanghai.

设$\overrightarrow{a}$ ，$\overrightarrow{b}$ ，$\overrightarrow{c}$ 是空间任意的非零向量，且相互不共线，则以下命题中：
①（$\overrightarrow{a}$ ·$\overrightarrow{b}$）·$\overrightarrow{c}$－（$\overrightarrow{c}$·$\overrightarrow{a}$ ）·$\overrightarrow{b}$ =0；

②$\left|\overrightarrow{a}\right|+\left|\overrightarrow{b}\right|>\left|\overrightarrow{a}-\overrightarrow{b}\right|$ ；

③若存在唯一实数组$\lambda ,\mu ,\gamma$ 使$\gamma \overrightarrow{c}=\lambda \overrightarrow{a}+\mu \overrightarrow{b}$ ，则$\overrightarrow{a}$ ，$\overrightarrow{b}$ ，$\overrightarrow{c}$共面；

④$\left|\overrightarrow{a}-\overrightarrow{b}\right|·\left|\overrightarrow{c}\right|=\left|\overrightarrow{a}·\overrightarrow{c}-\overrightarrow{b}·\overrightarrow{c}\right|$.
真命题的个数是（  ）

在复平面内，复数$\frac{i}{1-i}$对应的点位于（     ）