An engineering firm is developing a bridge for trains using recycled materials. It is building prototypes of the bridge to be tested. Which statement best explains why prototyping can be important? A. Building a prototype allows conductors to use the proposed bridge while it is still being tested.

B. Building a prototype allows all brainstormed bridge designs to be modeled.

C. Building a prototype allows the most promising bridge design to be tested in a safe manner.

D. Building a prototype allows the constraints for the bridge to be ignored.

In a unit cell of fcc structure, indicate the position of one of the tetrahedral interstitial sites by plotting the corresponding tetrahedron. do the same for one of the octahedral interstitial sites (in a separate fcc unit cell). mark the positions of all the tetrahedral and octahedral interstitial sites in the unit cells. how many equivalent tetrahedral sites and how many equivalent octahedral sites are contained in a fcc unit cell, respectively. what is the coordination number for a tetrahedral site and what is the coordination number for an octahedral site?