There is actually none.
0, but there are 2 commas if thats what you mean
There have been at least four periods of large-scale glacial activity during the last two million years.
They are both time periods of the early Paleozoic. The Ordovician was approximately 490 million years ago, to 440 million years ago. The Silurian was approximately 440 million years ago, to 416 million years ago. The Silurian was the period immediately after the Ordovician. The two periods were divided by the second largest Mass extinction in history.
About 250 million years, from 300m to 65m, spanning three periods(Triassic, Jurassic, and Cretaceous
The Ice Age.
The Cenozoic era has three periods. These periods include the Paleogene, the Neogene, and Quaternary. This era covers a span of 66 million years ago until present time.
The Mesozoic era took place 252. 17 million to 66 million years ago. The three major periods that make up the Mesozoic era are the Triassic, the Jurassic, and the Cretaceous periods.
Dinosaurs lived in the Mesozoic Era. This was a time between 230 million and 65 million years ago. The Mesozoic Era is divided into three time periods: the Triassic, Jurassic and Cretaceous periods.
There are 4 periods
If you look at it more carefully, or mark off the periods with commas, you'll see that what you have there is 2 million million, or Two trillion.
there are 4 marking periods
I think there is 1111111 periods in a life time
Californium hasn't "periods" inside.
unit, thousand, million billion and so on
It is now accepted in the UK that a billion is 1,000,000,000 (one thousand million), (it used to be 1,000,000,000,000 ie, one million million). We use the comma, though I believe the period is used in the USA? Therefore, where I've shown a comma, simply assume it is a period if you are in the USA!
there are four periods in basketball
The periodic table has 7 periods.
there are 7 periods in the periodic table118
2 periods are in a soccer game