Which of the Following Statements Is True About Vegetable Stocks

Which of the following statements is true about vegetable stocks?

A) The best times for cooking vegetable stocks are between 30 and 45 minutes.
B) Brussels sprouts, cauliflower, and artichokes produce a stock with a mild flavor and odor.
C) Unless green, leafy vegetables (such as spinach) are cooked for a long time, they develop an unpleasant flavor.
D) Sweating vegetables in a small amount of oil or butter before adding them to water gives them a sharper, more distinct flavor.