出现下列哪些情况时，需要修订基本标准成本（）。
A.产品的物理结构发生变化
B.重要原材料和劳动力价格发生变化
C.生产技术和工艺发生根本变化
D.市场变化导致的生产能力利用程度发生变化
参考答案：A, B, C
解析：基本标准成本是指一经制定，只要生产的基本条件无重大变化，就不予变动的一种标准成本。所谓生产的基本条件的重大变化是指产品的物理结构的变化，重要原材料和劳动力价格的重要变化，生产技术和工艺的根本变化等。只有这些条件发生变化，基本标准成本才需要修订。由于市场供求变化导致的售价变化和生产经营能力利用程度变化，由于工作方法改变而引起的效率变化等，不属于生产的基本条件变化，对此不需要修订基本标准成本。
| Natural flavorings and fragrances are often costly and limited in supply. For example, the vital ingredient in a rose fragrance is extracted from natural rose oil at a cost of thousands of dollars a pound; an identical synthetic substance can be made for 1% of this cost. Since the early twentieth century, success in reproducing these substances has created a new industry that today produces hundreds of artificial flavors and fragrances. Some natural fragrances are easily synthesized; these include vanillin, the aromatic ingredient in vanilla, and benzaldehyde, the aromatic ingredient in wild cherries. Other fragrances, however, have dozens, even hundreds of components. Only recently has it been possible to separate and identify these ingredients by the use of gas chromatography and spectroscopy. Once the chemical identity is known, it is often possible to synthesize them. Nevertheless, some complex substances, such as the aroma of fresh coffee, have still not been duplicated satisfactorily. Many of the chemical compounds making up these synthetics are identical to those found in nature, and are as harmless or harmful as the natural substances. New products must be tested for safety, and when used in food, must be approved by the U.S. Food and Drug Administration. The availability of synthetic flavors and fragrances has made possible a large variety of products, from inexpensive beverages to perfumed soap to used cars with applied "new car odor." |
Why does the author mention fresh coffee in Paragraph 2
A．As an example of complex substances having not been duplicated satisfactorily.
B．Because the coffee fragrance is hard to produce.
C．To conclude the passage.
D．The smell of fresh coffee is inviting.