An external factor that affects stem cells

specific cell source, donor age, plating density, passage number and plastic surface quality. Some other factors such as cell culture media and their supplementary factors, O2 concentration, mechano-/electro-stimuli and three-dimensional scaffolds are also shown to be influential.

it would be  

germany had to pay all damages related to the war.

and i think

germany had to take sole responsibility for the war.