本实验中绘制的靶刻度与—计数的关系曲线图中，下列描述正确的是？
A. 向下凹的区间，表示密度增大。
B. 向上凸的区间，表示密度增大。
C. 尖顶区间可能为圆柱体物体。
D. 平底区间可能为长方体物体。
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Which one of the following expressions can be used to introduce the superior quality and reasonable price of a product?
A. Our product is superior in quality and reasonable in price.
B. Our product is superior quality and reasonable price.
C. Our product is of superior in quality and reasonable in price.
Which one of the following expressions is used to introduce the function of a product?
A. The sofa is made with latest technology and professional design.
B. When you press the red button for 3 seconds, the mute function is activated.
C. If it's under warranty, you can enjoy free service.
When introducing the function of a product, which expressions or sentence patterns are often used? (multiple choice)
A. allow or help
B. by
C. time or conditional adverbial clauses
D. relative clause
Which expressions are correct to introduce the warranty of a product? (multiple choice)
A. If it's under warranty, you can enjoy free service.
B. If it's under warranty period, we offer free service.
C. If it's in the warranty period, we offer free service.
D. If it's in the warranty, free service is provided.
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