help with some astronomy questions?

I have a test coming up that I'm studying for and these are some of the questions I am not sure about if anyone could help me with any of them.

The center of the Galaxy was first discovered by

a. x-rays that it emits

b. radio waves that it emits

c. the intense light that comes from it

d. the bulge around it and the presence of old globular clusters that have gravitated toward the center of galaxy

e. It’s yellow glow

When we look at the sky on a dark, clear night, sometimes we can see a faint band of light stretching across it. What we are observing is

a) The plane of the Milky way Galaxy

b) Other galaxies

c) The stars of some other galaxy

d) Cluster of other galaxies that are drawn to the Milky way.

We have learned that the galaxy is a spiral galaxy by the

a) Emission of 21.1 cm hydrogen of light from nebulae

b) The Doppler shift of radio waves

c) Observation of globular clusters

d) Comparing ages of various clusters

e) Plotting the stars of various clusters on an H-R diagram

The 21.1 cm wavelength line is due to

a. The electron in the hydrogen atom moving from one orbital to another

b. The proton in the hydrogen atom moving from one state to another

c. The alignment of the magnetic domains in the hydrogen atom, namely the proton-electron interaction

From what is seen the arms further out that earth are moving

a) Away from us

b) Are moving toward us

c) The arms are faster near the center

d) The arms are moving faster near the outside

e) a and d

We deduce there are arms in the galaxy because

a) The radiation of the light (approximately 21.1 cm) is

b) Larger in wavelength near the edge of the galaxy

c) Shorted in wavelength near the edge of the galaxy

d) The intensity of the approximate 21 cm line varies in intensity radially

Thanks to anyone that can help!