题目

We now think of chocolate as sweet, but once it was bitter. We think of it as a candy, but once it was a medicine. Today, chocolate can be a hot drink, a frozen dessert, or just a snack. Sometimes it is an ingredient in the main course of a meal. Mexicans make a hot chocolate sauce called mole and pour it over chicken. The Mexicans also eat chocolate with spices like chili peppers. Chocolate is a product of the tropical cacao tree. The beans taste so bitter that even the monkeys say “Ugh!” and run away. Workers must first dry and then roast the beans. This removes the bitter taste. The wor如图，平面α⊥平面β，A∈α，B∈β，AB与平面α所成的角为，过A、B分别作两平面交线的垂线，垂足为A′、B′，若，则AB与平面β所成的角的正弦值是（   ）A．B．C．D．