Which european power was present west of the connecticut river as the puritans began to move westward?

The Dutch

Explanation:

The first European settlers in the Connecticut area were the Dutch. They had been in the area since 1614, but their first settlement was located at the site of Hartford. However, the same year that the settlement was established (1633), Puritans from Plymouth began to move into the territory of the Connecticut River. They encountered the Dutch, and the Europeans asserted their rights to the land. This caused the Puritans to move further north and establish themselves at Windsor.

yup! you are correct it is b.