Imagine an Advanced Civilization Living on a Planet Orbiting at a Distance

Multiple Choice

Imagine an advanced civilization living on a planet orbiting at a distance of 10 AU (1.5 billion kilometers) from a close binary star system that consists of a 15 MSun red giant star and a 10 MSun black hole. The black hole is surrounded by an accretion disk. Sometime within the next million years or so, the civilization's planet is likely to be doomed because .

A) jets of material shot out of the accretion disk will shoot down their planet
B) tidal forces from the black hole will rip the planet apart
C) the red giant star, which provides most of energy the civilization needs to exist, will soon be destroyed in the accretion disk
D) the planet's orbit gradually will decay, as it is sucked in by the black hole
E) the red giant will probably supernova within the next million years