The russians were able to establish a foothold in northern california (fort russ) because

No other European power had established a presence in the area.

In the early 19th century, Russia had already established some colonies in Alaska, securing its presence in America. Russia was expanding East, across Siberia, and eventually started moving south, until it reached Northern California.

Americans who were involved in the sea otter business proposed some joint hunting expeditions with Russian supervisors and Native Alaskan hunters to hunt seals along the Californian coast. These expeditions allowed the Russian parties to observe large stretches of uncolonized land. This led to the conclusion that a Russian settlement could be established in California.

answer; ///i believe that the correct answer is (b)arches and domes; ///

mosques-hypostyle halls with lots of space.towers called minarets flanks the luck