Which event may signal the development of a new black hole?
a. gravitational lensing
b. a gamma ray burst. c. matter accretion
d. a supernova

Which of these internal feedback reactions does not need your brain? oa. your leg jumping when it is hit by a reflex hammer b. your deeper breathing when you need more oxygen c. your body temperature rising when you have an infection d. your heart beating faster when you are in danger