1)When is/was gravitational contraction an important energy-generation mechanism for the Sun?
A)right after the Sun began fusing hydrogen in its core
* B)when the Sun was being formed from a collapsing cloud of gas
C)when the Sun transports radiation through the convection zone
D)only during solar maximum
E)only during solar minimum
2)What is the average temperature of the surface of the Sun?
* A)6,000 K
B)1 million K
3)From the center outward, which of the following lists the "layers" of the Sun in the correct order?
A)core, corona, radiation zone, convection zone, photosphere, chromosphere
B)core, convection zone, radiation zone, photosphere, chromosphere, corona
* C)core, radiation zone, convection zone, photosphere, chromosphere, corona
D)core, convection zone, radiation zone, corona, chromosphere, photosphere
E)core, radiation zone, convection zone, corona, chromosphere, photosphere
4)How do human-built nuclear power plants on Earth generate energy?