用所给动词的正确形式填空

    What a day! Yesterday, Ben____(run) to the bus stop. He____(drop) his schoolbag. He ____(pick) it up quickly but he didn't____ (pick up) his homework. He missed the bus so he ran to school.  Tony ____(find) Ben's homework and ____(shout) but Ben didn't____ (hear) him. He ____(carry)Ben's homework to school. There were lots of students at school.

  "I must ____(find)Ben!" said Tony. "BEN!"

  "Tony, you mustn't ____(shout) here."

  "Sorry, Miss Jiang. Can you see Tony?"

  "Yes, he's over there."

  "Thanks. "

  Tony ____(find) Ben and____ (give)him his homework.

  "Thanks a lot, Tony."

  "No problem, Ben."

数列｛a_n}满足$a_n=\left\{\begin{array}{c}n,n=2k-1\\ a_k,n=2k\end{array}\right.$，其中$k\in N^{*}$，设f(n)=a₁+a₂+a₃+...+a_2ⁿ-1+a_2ⁿ，则f(2013)-f(2012)等于(     )．

680L=____dm³=____m³

12/（____）=3÷4=（____）/12=15÷____ =____（填小数）