Beneath the soil of the Malheur National Forest in eastern Oregon, a fungus has for centuries been slowly weaving its way through the roots of trees, to become the largest living single organism known to humans.

• Ahas for centuries been slowly weaving its way through the roots of trees, to become  
• Bhas slowly woven its way through the roots of trees for centuries, and so becoming  
• Cthat has been slowly weaving its way through the roots of trees for centuries has become  
• Dthat has for centuries slowly woven its way through the roots of trees and has become  
• Ethat, having slowly woven its way through the roots of trees for centuries, to become