Acidic foods, such as tomatoes or wine, are important in a braise to

a. reduce cooking time
b. add a traditional flavor.
c. tenderize the meat.

B. and C.

Explanation:  

Braising (derived from the French word "braiser") is a combination-cooking method with moist heat commonly in a covered pot with a small amount of liquid. The result of braising is a particular flavor.

Acidic element in the liquid is often added to Braises. Because of the flavors wine adds to dishes, many cooks use wine instead of mere water.  Good choices as well are chicken or beef stock, tomato juice, beer or any other combination of two or more of these liquids. You should try balancing wine or beer with a stock to keep the flavors well rounded. A bit of acid will lighten a very rich, heavy dish. Also, it will bring out the subtle sweet or salty undertones.

If the food you’re braising won’t produce enough liquid of its own, a certain amount of cooking liquid that includes an acidic element added to the pot will help with this as well.

Acids can also tenderize the meat by breaking down fibers in foods that are cooked in it. As it tenderizes, it also penetrates and flavors the food. When preparing your dish, choose an acid which flavor will tribute to the rest of the meal.

c. shubert i think : )