So the frequency is f =10 cycles / 120 s = 0.0833 cycles/s. Answer: D. Frequency refers to the number of occurrences of a periodic event per time and is measured in cycles/second. In this case, there are 10 cycles per 2 minutes (also known as 10 cycles per 120 seconds).
From the scientific viewpoint, the Earth would have had to form about 4.54 billion years since the earliest material in the solar system is dated back to about this time period.
How long does it take to form? The time needed to form a soil depends on the latitude: in environments characterized by a mild climate, it takes 200-400 years to form 1 cm of soil; in wet tropical areas soil formation is faster, as it takes 200 years; in order to accumulate enough substances to make a soil fertile it takes 3000 years. For these reasons the soil is considered as a non-renewable resource: once it has been destroyed, it is lost forever.