Use this stimulation link to answer the questions.
https://pbslm-contrib.s3.amazonaws.com/WGBH/arct15/SimBucket/Simulations/standingwaves/content/index.html

Be sure that “Real Time” is highlighted in yellow, and that you have clicked the “hide blue wave” and “hide orange wave” boxes.  The “Start Node” box should also be selected.  The “Frequency” slider should be set to 0 Hz and the “Wave Speed” slider should be set to 100 cm/s.