Which describes a major challenge facing the builders of the transcontinental railroad?
tunneling under lake erie
crossing the sierra nevada mountains
bridging the rio grande river
spanning the grand canyon

north atlantic treaty organization.

aug 15, 2012 - although van leeuwenhoek was not the inventor of the microscope, he advanced it more he loved to grind and focus a new lens in order to see the unseen world. most of leeuwenhoek's microscopes were silver. in a simple but significant experiment (1668), he demonstrated that worms found on

the han greatly expands the chinese empire. the han dynasty retains the centralized bureaucracy and unified political system of the qin but adopts and grafts upon this the confucian view that government should be run by educated, ethical men.

explanation:

1. explain aspects of the democratic process as it was developed in ancient athens

2. trace the roots of the americans political process to ancient athens

3. explain the relationship of citizens to the political process