Which of the following is true about processes that shape the earth?
a.
only one process shapes the earth in a way that humans can notice.
b.
some processes that shape the earth are happening so slowly they cannot be easily detected in a human's lifetime.
c.
although there are many different processes that shape the earth, none of the processes can be observed by humans.
d.
all processes that shape the earth begin and end within a person's lifetime.