Final answer:
The most valuable possession in North America for England and France was the St. Lawrence Valley.
Step-by-step explanation:
England and France considered the most valuable possession in North America to be the St. Lawrence Valley. This region played a significant role in the rivalry between England and France during the colonization period. Both countries sought control over this area due to its strategic location and access to important waterways like the St. Lawrence River. The St. Lawrence Valley was highly sought after for its economic and military advantages, making it a valuable possession in the eyes of England and France.
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