You are on a guided tour looking at stone statues from historical events. you observe that the newer statues are the same color, but seem to be much sharper and have more detail than the others.

which explanation best explains these differences?

a
acid rain has dissolved the older statues over time.

b
wind has slowly broken aways bits of the older statues.

c
dirt and pollution has covered the features of the older statues.

d
animals have probably scratched away at the older statues of time.