虽然解决了桥梁构造设计的难题，实际建造中仍然面临许多困难。

A.Although we have overcome the problem of the design for the structure of the bridge, we still confront many difficulties concerning its actual construction.

B.Although the problem of the design for the structure of the bridge has been overcome, we are still confronted with many difficulties concerning its actual construction.

正确答案：Although the problem of the design for the structure of the bridge has been overcome, we are still confronted with many difficulties concerning its actual construction.