Can you suggest a reason why historians see Marston Moor as a ‘turning point’ in the civil war?

The correct answer to this open question is the following.

Although there are no options for this question we can say the following.

Historians see Marston Moor as a ‘turning point’ in the civil war because this was the largest battle regarding the number of troops, to be fought in England during the English Civil War (1642-1651). Historians think that according to some sources, the Parliamentarian and Scots troops killed approximately 4,000 Royalists soldiers.

The victory of the Parliamentarian and Scots meant one thing but an important one in the Civil War: the Royalists had lost total control of the North part of the English territory.

Historians also consider that the victory impulsed the career of military official Oliver Cromwell.

i am sure the answer is d