With no explanation, label text_A→text_B with either "not_related" or "related".
text_A: Extreme environments can only be caused by humans.
text_B: State Highway 4 or SH 4 is an east -- west state highway that runs from the Gateway International Bridge in Brownsville to the Gulf of Mexico at Boca Chica State Park .. Mexico. Mexico. Boca Chica State Park. Boca Chica State Park. Brownsville. Brownsville, Texas. Gulf of Mexico. Gulf of Mexico. Outside of Brownsville , it parallels the Rio Grande .. Brownsville. Brownsville, Texas. Rio Grande. Rio Grande. It is the southernmost Texas state highway .
not_related.