I think the correct answer would be that <u>they condensed out of hot gas clouds surrounding the early sun.</u><span />
Answer:
the phase difference is 1.26 radian
Solution:
As per the question:
Distance, d = 2 m
Distance from the other speaker, d' = 2.1 m
Frequency, f = 680 Hz
Speed of sound, v = 340 m/s
Now,
To calculate the phase difference,
:
Path difference, 
For the wavelength:

where
c = speed of light in vacuum
= wavelength
Now,


Now,
Phase difference, 

The law of conservation of mass states that mass can be destroyed during a chemical change is TRUE