A、Com and sugar cane. B、Rye and corn. C、Strong beer and wheat. D、Rice and wheat. C新闻的结尾提到，制成威士忌后，剩下一两个没什么用处的废产品：strong beer和whea

[3]Waste products from a popular alcoholic drink could be used in the future to make biofuel. Researchers say the new fuel, based on whisky, could reduce demand for oil. They say using less oil could cut pollution that studies have linked to climate change.
    Scotland is the largest producer of whisky in the world. And a Scottish professor has found how to take the waste products from distilling whisky and turn them into a form of alcohol called biobu-tanol. Biobutanol can be used as a fuel. Whisky comes from grain, such as corn and wheat.
Martin Tangney is director of the Biofuel Research Centre at Napier University in Edinburgh. He says less than 10 percent of what comes out can be considered whisky. [4]The rest is mainly one of two unwanted products: strong beer and wheat. Tangney says the two byproducts can be produced to create a new material: biobutanol.
3. What is the news report mainly about?
4. What are the unwanted products in making whisky?