I think C. Mutualism.
Hope this helps :)
Answer:
History is the study of the past in all its forms. Philosophy of history examines the theoretical foundations of the practice, application, and social consequences of history and historiography. It is similar to other area studies – such as philosophy of science or philosophy of religion – in two respects.
Explanation:
As we know that there are avogadro no. of atoms in 9 g of beryllium.
1 mole of beryllium = 6.02 * 10^23 atoms
so 2.5 mole= 6.02*10^23*2.5 i.e = <span>15.055 × 10^23 atoms </span>