Which of the following is least likely to be considered an input to production?

The business cycle ________ on Delta Airlines since the company's inception over 80 years ago

A) has always had a negative effect B) has had virtually no effect C) has always had a positive effect D) has had a large effect

When calculating the TSLS standard errors

A) you do not have to worry about heteroskedasticity, since it was eliminated in the first stage B) you can use the standard errors reported by OLS estimation of the second stage regression. C) the critical values from the standard normal table should be adjusted for the proper degrees of freedom. D) you should use heteroskedasticity-robust standard errors.