Great Britain and France responded to Hitlers invasion of the Sudetenland by doing what

They both decided to declare war on Germany in 1939.

Explanation:

this is what was decided by so-called Munich crisis (October 1938): Italy, England, France and Germany. They decided to give Hitler Sudetenland without a war to assure peace for themselves.

Explanation: This strategy did not work out because this strategy was motivated by fear. Germans occupied Sudetenland and then created Protectorate Bohemia and Moravia.

i confess that there are several parts of this constitution which i do not at present approve, but i am not sure i shall never approve them: for having lived long, i have experienced many instances of being obliged by better information or fuller consideration, to change opinions even on important subjects, which i once thought right, but found to be otherwise. it is therefore that the older i grow, the more apt i am to doubt my own judgment, and to pay more respect to the judgment of others.