Answer : The frequency decreases by a factor of 2.
Explanation :
Given that the wave travels at a constant speed. The speed of the wave is given as :

Where
υ is the frequency of the wave 
and λ is the wavelength of the wave.
In this case, the speed is constant. So, the relation between the frequency and the wavelength is inverse.

If the wavelength increases by a factor of 2, its frequency will decrease by a factor of 2.
Hence, the correct option is (A) " The frequency decreases by a factor of 2 ".
 
        
                    
             
        
        
        
Answer:
23.67 km / hr
Explanation:
car travels 355 km (d)
duration = 15 hrs  (t)
average speed formula = v = d / t
v = 355 km / 15 hr
v = 23.67 km / hr
 
        
                    
             
        
        
        
3.4m/s 
Explanation:
Given parameters: 
Distance to school  = 14.4km
Time taken by Amy = 49min
Time taken by bill = 20min after Amy = 20+49 = 69min
Unknown parameters: 
How much faster is Amy's average speed = ? 
Solution: 
Average speed is the rate of change of total distance with total time taken. 
  Average speed = 
convert units to meters and seconds
       1000m = 1km 
        60s = 1min
Distance to school  = 14.4 x 1000 = 14400m 
Time taken by Amy = 49 x 60 = 2940s
Time taken by Bill = 69 x 60 = 4140s 
Average speed of Amy =  = 4.9m/s
  = 4.9m/s 
Average speed of Bill =  = 1.4m/s
  = 1.4m/s 
Differences in speed = 4.9 - 1.5 = 3.4m/s 
Amy was 3.4m/s faster than Bill 
learn more: 
Average speed brainly.com/question/8893949
#learnwithBrainly
 
        
             
        
        
        
Answer:
The answer is D the rising of warm air pushing down cool air.