Answer: C. The time taken for the light to travel would have been too little to have been measured by them.
Step-by-step explanation:
Light travels at a speed of 300,000 km per second which is much too fast for the naked eye to even comprehend. This is why light shinning in a distance is picked up instantaneously by out eyes.
This experiment done by Galileo would therefore be unable to measure the speed of light because the light from either lantern would have traveled too fast for Galileo to be able to measure the time taken.