Which policy or initiative contributed most to the nuclear arms race between the united states and the soviet union

The policy contributed most to the nuclear arms race was Mutual Assured Destruction

This means that both sides knew that any attack upon the other would be devastating to themselves, therefore restraining them from attacking the other. Each side possesses enough nuclear weapons to obliterate the other side that causes them to restrain from attacking afraid of the annihilation.

d. migration of french settlers into english colonies

c it says nothing about connecting those 2 seas.