Answer:
C. Repeat sign
Step-by-step explanation:
In music, when there is a colon followed by two lines, it indicates that you repeat. When you reach the repeat sign, go back to either:
a) The beginning of the piece; or
b) The "open" repeat sign, which looks like the one in the picture, but it's backwards.
A. An accent sign is a symbol that goes above a note.
B. Final barline can easily be confused with the repeat sign. It is one thin line followed by a thick line, like in the picture but without the two dots.
D. Sometimes people call a double barline the end of a song, but a double barline is two thin lines. Usually, there is a pause for the end of a section and the song continues after the pause.