Blended scotch whiskies must contain which of the following?

Blended scotch whiskies must contain a combination of malt whiskies and grain whiskies sourced from different distilleries. This blending process is essential to achieve the desired flavor profile, complexity, and consistency that defines a blended Scotch whisky. By incorporating both malt and grain whiskies, distillers can create a balance of flavors – the malt whiskies typically provide depth and character, while the grain whiskies contribute smoothness and affordability.

The other options focus on different types of whisky that do not accurately describe what blended Scotch whisky is. For example, single malts refer to whisky produced at a single distillery using malted barley, and they do not involve blending with grain whisky or other distilleries. Exclusively grain whiskies would mean a product made only from grain without any malt component, which is not characteristic of blended Scotch. Additionally, the stipulation regarding aging for at least 10 years is not exclusive to blended Scotch, as the legal requirement for any Scotch whisky is a minimum aging period of three years. Thus, option A accurately captures the essence of blended Scotch whiskies.