You asked the question twice I answered it on the last one
Answer:
the time it takes for one complete back and forth swing
Explanation:
the Mark's is showing you the time it swings back and forth
Answer:
a

b

c

Explanation:
From the question we are told that
The frequency is 
The length of the vibrating string is 
The mass is 
Generally the wavelength is mathematically represented as

=> 
=> 
Generally the wave speed is

=> 
=> 
Generally the tension on the wire is mathematically represented as

=> 
=> 