d. 1 method can only apply for invention. 2. The powder has no specific shape structure. If it can be formed into a fixed shape through other devices, it can be applied for practical use, such as mercury in a thermometer. 3. The granular shape is not clear, and the material is not the subject of practical protection. If the material is known, has a specific structure or is used in specific products, it can apply for practical use. If it is not stated in the option, it will be deemed not to fall into the above situation. In fact, in actual processing, granular materials can be applied for practical use, but this is not what the questioner meant in this question. Option c is just a personal opinion, please give advice from experts.