Which of the following would most likely be considered a primary source document?
a. a collection of raw data from an important research study
b. a story in the newspaper on the history of the automobile
c. an interview with a professor who is an expert in ancient engravings
d. an article in a periodical that sums up recent developments on an issue

A primary source is a direct source for some information, not in interpretation or someone re-telling the information in the source - the latter is a secondary source.

Here answers B, C and D present secondary sources, where someone uses information available somewhere else.

The correct answer is: a collection of raw data from an important research study (A)

It turns into vapor and goes into the atmosphere