The article implies a causal link, with gaining father's acceptance (the explanatory variable) resulting in better grades (the response variable). Which of the remaining six reasons for relationships between variables (reasons 2 through 7) could explain the observed connection

Adouble-strand no. 60 roller chain is used to transmit power between a 13-tooth driving sprocket rotating at 300 rev/min and a 52-tooth driven sprocket. a) what is the allowable horsepower of this drive? b) estimate the center-to-center distance if the chain length is 82 pitches. c) estimate the torque and bending force on the driving shaft by the chain if the actual horsepower transmitted is 30 percent less than the corrected (allowable) power.