Answer:
Intensity at 45 cm will be 0.2283 volt
Explanation:
We have given that intensity of signal measured by the detector is 0.74 volt at a distance of 25 cm
We know that intensity of signal is given by
, here s is strength of light and r is distance
So 

In second case
Intensity is given by 
So 
100m ÷ 50s = 2m/s
Just some simple divison.
The correct answer is C. more mass and less distance between two objects.