First, a reminder: this is not really a test of your knowledge; no one is expected to know these things unless they have studied them! So don't fret if you don't know, just guess and we'll give you the answer and explain it. Expect the entire quiz to take 15 to 20 minutes.
The first thing about the income tax to get straight is what kind of thing is being taxed.
The subject of the income tax (the thing upon which the tax is laid) is: