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在光电断续器中,光的发射器、接收器做在体积很小的同一塑____壳体中,所以两者能可靠地对准,为安装和使用提供了方便,它也可以分为遮____型和反____型两种。

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Listen to the dialogue between Mr. Li and Mr. Brown in the Exhibition Hall at the China Export Commodities Fair and choose the best answer to each question.[音频]What is Mr. Li boasting about when Mr. Brown appears in front of his booth?

A. Trousers.
B. T-shirts.
C. Suits.

What advantages does Mr. Li NOT mention about his products?

A. They are modern and elegant in style.
B. They are classic in style.
C. The material retains its luster without becoming shiny.

How many colours do Mr. Li's samples have?

A. 5.
B. 6.
C. 7.

What size does Mr. Li NOT have?

A. S.
B. M.
C. XXXL.

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