What is true about certificates of deposit?

they offer lower interest rates than savings account.
they are the most liquid account available.
the money has to remain in the account for a specified period of time.
all of the above are true.

For a science project, a high school research team conducted a survey of local air temperatures. based on the results of the survey, the found that the average temperatures were around 10 degrees higher than expected. this result was wrong. the trouble with the survey was that most of the locations were exposed to direct sunlight and located over asphalt or sand, which resulted in higher temperatures than normal. this is a classic example of an error in which phase of inferential statistics?