—         purple.

阅读下面短文，根据所读内容，在文章后的小题大空格里填入一个最恰当的单词。 注意：每个空格只填1个单词。

    PowerPoint Presentations（PPT） are taking the place of writing on the blackboard with chalk. Someday, will robots take the place of human teachers?

    In Japan, a robot is going to enter classrooms to help teachers. Last week the Japanese company Honda Motor Co. showed the public its robot at a Tokyo museum. The robot's name is Asimo. Students will see Asimo in science classes and learn the wonders of science.

    Asimo is 130 centimeters tall with a round head. It can jog, walk up stairs and wave. It can also avoid（避开） things on its way and have simple talks with you. Asimo is an experienced worker for humans. It has worked as a guide in showrooms. But this will be the first time it works as a teaching assistant in classrooms and in formal teaching!

    How will Asimo help in class? A teacher explained the way Asimo works to students in last week's show. Asimo has sensors（感应器） inside its body to keep its balance.

    The smart Asimo tilted（倾斜） its body when it stood on a shaking platform（平台）. Asimo kept its balance. But a wooden person beside Asimo fell (See the above picture).

    When you walk, you pass your weight from the heel to the toe. The Japanese teacher explained this with Asimo at the museum. He moved the robot in slow move. Asimo made learning science more interesting for students!

    Asimo will soon help teach thousands of primary students and junior high schools in two Japanese cities. Hopefully, robot teachers will arrive in our classrooms in China one day.

—I'm afraid I can't. I have much homework _________.

—Mary.