What innovation or invention made suspension bridges possible.?

Bessemer process

Explanation:

The Bessemer process is a process of removing impurities from iron through oxidation. this process is used to make the iron stronger this stronger iron will in turn used to make stronger steels which will be used to make better rails for transportation.

suspension Bridges are made up of steels, and this steel has to be very strong to suspend a bridge hence the innovation/invention of the Bessemer process which brought about the production of very strong steels through the process has helped the suspension of bridges. steels produced from Bessemer process is also used in the construction of rail ways and very high rising buildings.

i believe the correct answer is option b. most eastern european nations joined nato.

though i could be wrong, option d. the eastern european nations were granted complete independence, would be another choice.

hope this ! : )