Solve this riddle: What English word has three consecutive double letters?

How to build a cardboard bridge busing no tape or glue only cardboard and only be allowed to cut the cardboard and it has to be a beam bridge?

Atype of construction where tha main load bearing element are hung for suspension cables that are then suspended from vertical supports anchored into the ground or a riverbed

Which of the following is necessary to build a skyscraper? a. wooden beams b. metal beams c. plastic supports d. all of the above