若向量$\overrightarrow{a}$与$\overrightarrow{b}$不共线,$\overrightarrow{a}·\overrightarrow{b}\ne 0$,且$\overrightarrow{c}=\overrightarrow{a}-\left(\frac{\overrightarrow{a}·\overrightarrow{a}}{\overrightarrow{a}·\overrightarrow{b}}\right)\overrightarrow{b}$,则向量$\overrightarrow{a}$与$\overrightarrow{c}$的夹角为(    )

根据短文内容，从A、B、C、D四个选项中选择正确答案。

    Years ago, when Dad moved to the USA, I had to go to school in New York. I was worried.  How could I, an eight-year-old girl from 1, make friends in America?

    On my first day at Anna Silver School, I met Miss Green, my class 2. She spoke to me slowly and 3 to get me used to her American accent. When she discovered that I 4 drawing, she encouraged me a lot. Miss Green made sure that I could fit into her class easily, and before I knew it, I was already having 5 fun, just as other schoolgirls could.

    When Dad was sent back to India, I had to6 Anna Silver School.  I was 7 again Miss Green had planned to take us students for a 8 trip, but I had to say goodbye to them now.  So, with a 9 heart, I left my school and the USA.  Back in India, I received a package one day.  It was 10 Miss Green and my 24 classmates. They had written me a letter each, 11 me about the fishing trip. Miss Green said she 12 me very much. With her good wishes, she added, "Keep up with your drawing 13 you love it so much."

    I'm very 14 to Miss Green. She not only made a shy little 15 feel at home in a faraway country, but also taught me and my classmates to understand the importance of being kind to others at an early age.

称取NaCl和BaCl₂的固体混合物32.5g，加入100g蒸馏水，完全溶解后向该混合溶液中逐滴加入质量分数为10%的Na₂SO₄溶液，反应生成BaSO₄沉淀的质量与所加入的Na₂SO₄溶液的质量关系如图所示．试回答下列问题：（提示：BaCl₂+Na₂SO₄═BaSO₄+↓+2NaCl）

实验过程：①关闭Ⅰ、打开Ⅱ；②关闭Ⅱ、打开Ⅰ．

下列说法不正确的是（   ）