Natasha holds the two ends of a string in her hands and then moves her hands up and down so that a wave travels from one end of the string to the other end. in which case will she have a standing wave along the string?

a. the resultant wave rises and falls in amplitude over time and has a frequency equal to that of the waves.

b. the resultant wave has a fixed amplitude and a frequency twice that of the waves.

c. the resultant wave has a fixed amplitude and a frequency equal to that of the waves.

d. the resultant wave rises and falls in amplitude over time and has a frequency twice that of the waves.