标板装在穿过管壁的支撑上。
The target is mounted on a support passing through the pipe wall.
请注视视标板，你能发现哪一个数字的背景颜色更亮吗？
Please watch the test-object board. Can you find which number has the brightest background color?
请注视视标板，你能发现哪一个数字的背景颜色更亮吗？
Please watch the test-object board. Can you find which number has the brightest background color?
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