The answer is D. Either absorbed or reflected. The reason is because if no light is being shown on the other side, the substance is not letting any light pass through. Since we do not know anything else about the substance, we do not know which one of the two it is doing. The scientist would not see any light on the detector if 100% of the light is reflected and the same thing would happen if 100% of the light was absorbed.
To solve this problem we will apply the linear motion kinematic equations. With the data provided we will calculate the time of the first object to fall. Later we will get the time difference between the two. This difference will allow us to find the free fall distance. Through the distance we will find the initial velocity, that is,



The second object is thrown downward at one second later and it meets the first object at the water is


The distance of the object will travel due to free fall acceleration is



The distance of the object will travel due to its initial velocity is




Therefore the initial speed of the second object is 21.06m/s
Answer:
46,800 seconds. I hope this helps