The author develops the central idea that theremin is unlike most conventional musical instruments by describing the A. Decline in popularity of the instrument
B. Way the instrument is built as a hobby
C. unique appearance and way of playing the instrument
D. unique sound and use of the instrument in movie soundtracks

C. unique appearance and way of playing the instrument

Explanation:

Theremin is a music instrument that is very unconventional in terms of the way it is played and in its appearance. It is a type of instrument that uses electricity for its operation. The musician do not physically play the instrument. There are two metal antennas to control the volume and the pitch of the music. This instrument was invented by Leon Theremin in 1920. He was a physicist from Russia. The music was created by the movement of the hands of the musician where the electric signals are created.

whats the question> > ?

ok so like i went to wiki and looked up the (constitution x new "hammystan")and it showed me the picture it highlights new hampshire and says first and second session and than it says that they hit up the u.s and was like "ey dude that paper u sent us was adopted it bro thx" xd syays it all on wiki/the pic

i dont really like reading so i guess other people might not like reading either so   imma put the answer in bold italics