Which factor best completes this diagram?
A.A decline in agricultural production
B.The growth of labor unions
C.New transportation systems
D.Increased government regulation
![Which factor best completes this diagram AA decline in agricultural production BThe growth of labor unions CNew transportation systems DIncreased government reg class=](https://us-static.z-dn.net/files/dbb/f28be7803d9f5bfe9b72983aef8c2e2b.png)