Answer:
D By looking all the way to the cosmological horizon, we can see the actual conditions that prevailed all the way back to the first instant of the Big Bang.
Explanation:
Astrophysicists are able to determine the conditions that existed in the early universe, by using instruments such as telescopes to observe and study cosmic horizons. More ideas about the early universe can be found from the thermal light present in cosmic backgrounds.
Scientists study these details that provide an insight into the conditions that existed so many years ago. They have been able to determine that the Big Bang involved so many collisions from these observations.
The answer is:
V = d/t d = 86 km t = 1.3 hrs
V = 86 km/ 1.3 hrs
V = 66.15 km/ hrs
I hope this helps!!
To solve the exercise it is necessary to take into account the definition of speed as a function of distance and time, and the speed of air in the sound, as well

Where,
V= Velocity
d= distance
t = time
Re-arrange the equation to find the distance we have,
d=vt
Replacing with our values


It is understood that the sound comes and goes across the entire lake therefore, the length of the lake is half the distance found, that is



Therefore the length of the lake is 634,55m
I think one hour, sorry if i'm wrong