Dr. paul found that college students between the ages of 18 and 23 performed better on a cognitive task in a low-noise condition than in a high-noise condition. dr. ben wants to repeat dr. paul's study by adding age as a variable—18-23 and 65-74. he predicts an interaction between the age and noise variables. in this case, dr. ben is questioning the validity of the original study.

external

Explanation:

The process of applying the conclusion of a particular scientific study into a study which is outside its context is said to be external validity. The conclusions derived in one particular study is applied to other situations through external validity. There are cases when such generalization brings a negative result to the study. Also, the factor of generalization is limited to some extent.

d. the polar jet stream   lies between the polar easterlies and trade winds should be your answer