根据下面对话  中的情景,在空白处填入适当的单词,使对话内容完整.每空一词。

A :Let's play tennis.

B: That 1________interesting.  Where is your tennis?

A: It's under the desk. 2______ you have a tennis racket?

B: No,I don't.I have a soccer and a volleyball, but I 3______have a tennis racket.

A: Does your sister 4______ a tennis racket?

B: No, she 5______.She plays baseball.

A: Oh, then let's play baseball. It's fun, too.

对频繁改变观察距离，不断变换瞄准目标的作业，改善照明条件有助于扩大调节范围，提高调节的准确性，增加照明能够提高不同距离上的辨认速度，并且能使作业者减少疲劳。对视觉紧张作业，常从近处向远处瞄准，也会减轻疲劳。视觉工作距离不应小于（）调节近点。