听力原文： These are the so-called killer Bees you've no doubt heard about. Africanized Honey Bees are the same species as the familiar European honey bees used to produce honey and pollinate crops, but they're different subspecies. They are called "Africanized Honey Bees" because they are the result of interbreeding between European bees and bees from Africa, which were inadvertently released in Brazil in the 1950's. They have also been referred to as "Killer Bees" in the media because of their increased defensive behaviors. Africanized Honey Bees came from the southern part of Africa. They were brought to southern Brazil, and have since spread as far south as northern Argentina, and northward throughout South and Central America, and Mexico. They entered the United States in southern Texas in 1990, Arizona, and New Mexico in 1993 and California in 1994. Many people expect Africanized bees to be larger and very distinctive, but in fact, they look nearly identical to the European Honey Bees. Africanized bees are about 3/4 inch long, brownish, and a little fuzzy. These bees are not ferocious until something disturbs them.
Why are the bees called "Africanized Honey Bees"？

A. They are defensive when they feel threatened.
B. It is the interbreeding between European bees and African bees.
C. They came from the southern part of Africa.
D. They are so large.