任务型阅读

    This is Ken. He likes pandas best. ①Because he thinks pandas are smart. Pandas are from China. His friend Tom is different from(与……不同) him. Tom's favorite animals are giraffes because he thinks they are very cute and friendly.

    I like tigers. I think they are beautiful and energetic（充满活力的）. But now the tigers, especially（特别）the Manchurian tigers(东北虎), are in great danger. We must save them.

    We love animals. ②We think people should protect（保护）all the animals.

② $—\text{CHO+}—\begin{array}{c}\text{H}\\ ｜\\ C—\\ ｜\\ \text{CHO}\end{array}\text{H}\stackrel{稀\text{NaOH}溶液\text{/}△}{\underset{}{\to }}\text{CH=}\begin{array}{c}｜\\ \text{C}\\ \end{array}—{\text{CHO+H}}_{\text{2}}\text{O}$

请回答下列问题：

如图，四边形ABCD内接于⊙O，若它的一个外角∠DCE=70°，则∠BOD=（　　）