请在下面几个相同含义的句子中，选择出你认为是formal expression的句子：

A、There are some studies that have concluded that bamboo could be used by builders more widely than it is now as a construction material.;

B、Some studies have concluded that bamboo could be more widely used than it is now as a construction material. ;

C、Bamboo could be used by builders more widely than it is now as a construction material is concluded by some studies.;

D、According to a number of recent studies, it is feasible to increase the use of bamboo in the construction industry