When you do exercises, your heart works better. It is able to______ more blood while beating more slowly. A. produce B. pump C. increase D. bump 答案:B“泵入更多的血”。 A. “产生”;C. “增加”;D. “碰,撞”。 19.已知向量$\overrightarrow a$=(1,m),$\overrightarrow b$=(2,m-3),且$\overrightarrow a⊥\overrightarrow b$,则实数m的值为1或2.