Briefly describe the threat in the context of the study description,

INSTRUCTIONS:  Referencing Internal Validity, please pick one of the studies listed below and (1) Briefly describe the threat in the context of the study description, (2) name the threat, and (3) explain how internal validity is threatened.

Original Study:

Tv ads promote online “brain games” and learning tools for adults and kids. A researcher decided to test the effectiveness of one of these games, ABCmouse. She gave kids aged 3-5 experience with either ABCmouse or an alternative game that wasn’t educational (Pig Pile). After giving kids 2 weeks of experience playing their respective game, she tested their reading ability using the Burt Reading Test, which tests how many of 110 words a child can read. The words are graded in order of difficulty, so the more words children can read, the better their score. She was able to use students at a large, public preschool as participants. All the kids were aged 3 to 5.