The development of Georgia's railroad system and the introduction of the cotton gin were similar in that

hygrometers and hair thermometers (often found as part of hygrometers/psychrometers) can be used to measure humidity. barometers are used to measure atmospheric pressure, while anemometers are used to measure wind speed. so the 2nd and 4th choices should be the correct answers.

answer; longitudinal;

answer; control group;

answer; use multiple stimuli;