Which of the following best describes base malt?

Base malt is best described as lightly kilned and containing enzymes, which make it essential in the brewing process. It serves as the primary source of fermentable sugars during mashing, providing the backbone for most beers. The enzymes present in base malt, predominantly amylase, are crucial for converting starches into sugars, enabling fermentation by yeast.

The characteristic of being lightly kilned allows base malts to have a moderate flavor profile that can be easily complemented by other specialty malts. This attribute is important because base malts are used in larger quantities than specialty malts, making their characteristics foundational to the beer's style.

In contrast, the other choices focus on different attributes that do not align with the defining qualities of base malt. Dark or rich flavors and colors are typically associated with specialty malts. When discussing diastatic power, it refers to the malt's ability to convert starches into fermentable sugars; a malt low in diastatic power would not serve effectively as a base malt, as the primary role of base malt is to support this conversion. Thus, option B accurately encapsulates the essence of base malt in brewing.