Final answer:
Northwestern Europe predominantly experiences a Humid Oceanic climate (option B) due to the moderating effects of the Gulf Stream, which results in moderate temperatures and distinct seasonal changes.
Step-by-step explanation:
The climate found in most of northwestern Europe is Humid Oceanic (option B). This climate is influenced by the Gulf Stream, which brings warmed waters from the Gulf of Mexico across the Atlantic to Europe, contributing to a temperate climate despite the northern latitudes. Areas with type C climates, including Western Europe, experience pronounced seasonal changes with cool to cold winters and warm summers, and can have low to high precipitation levels. In contrast, type D climates are colder and found more inland or at higher latitudes, and are not characteristic of northwestern Europe.