The main factor that slowed construction of the central pacific railroad was a shortage of supplies, which had to be shipped around south america. intense summer heat that melted the railroad ties and tracks. scarcity of wood used for building railroad ties and trestles. conflicts with american indians who closed down the tracks.

The correct answer is a shortage of supplies, which had to be shipped around South America.

Although the government gave land to the railroad companies to accelerate the development of a transcontinental railroad, there was still a challenge of supplies which slowed down the construction

id say bottom left to top top left to bottom right and middle to middle

explanation:

b. florence

d. milan