An index:

a. combines two or more metrics into a single indicator
b. is complex to define, usually involves a calculation and is often in the form of a ratio
c. is easily defined with no calculations and with simple dimensions
d. is any quantitative output of an activity or process

Which sentence best represents the thesis of this article? a they challenge us to consider whether we can trust what we are seeing. b optical illusions may seem mysterious, but they are not unexplainable. c through science, we can learn how optical illusions work. d let’s take a look at three common optical illusions and explore the science behind each one.

The american public was excited by the invention of the railroad system. true false

The platt amendment of 1901 forbade cuba from entering into any treaties that would allow undue foreign involvement in cuban affairs. this law was passed after the spanish-american war to make sure that european nations weren’t going to get involved with cuba. 1, why might the platt amendment be considered ironic? 2, what reasons would the united states have for not wanting european influence in cuba?