The correct option is D
All of the above
Steps to construct a stethoscope at home:
1) Take a funnel and put its small end at one end of the flexible tube. Push the funnel as far as u can into the tube.
2) Tape the funnel using suitable tape.
3) Inflate the balloon to stretch it out. Let the air out and then cut the neck of the ballon.
3) Stretch the remaining part of the balloon tightly over the open end of the funnel, and tape it. This creates the tympanic membrane for the stethoscope
4) Place the funnel end of the stethoscope on to the chest and end of the tube to the ear to listen to the heartbeat.
Hence rubber tube, balloon and funnel can be used to make a stethoscope at home.
So, the correct answer is 'All of the above'.