<span>Science is orderly knowledge proven by experimentations.</span>
Answer:


Explanation:
Wave 1, 
Wave 2, 
Wave 3, 
Wave 4, 
The general equation of travelling wave is given by :

The value of
will remain the same if we take phase difference into account.
For first wave,



For second wave,



For the third wave,



For the fourth wave,



It is clear from above calculations that waves 1 and 3 have same time period. Also, wave 2 and 4 have same time period. Hence, this is the required solution.
15 because i did the math, had this assignment, and also watch a video
C, the two samples are in different states!