Emma is planning an experiment to examine whether reading to children increases their vocabulary size. she plans to measure the vocabulary size of a group of 18-month-old children, read to them three times a week for 3 months, then measure their vocabulary size again. which threat to internal validity should she be most concerned about

   She could add a comparison group

Explanation:  Emma will conduct an experiment with children 18 months of age and read to them three times a week for three months and then measure their vocabulary, although without reading, the vocabulary will change in three months, naturally. Therefore, in order to determine the impact of reading on vocabulary change, Emma should also have a comparable group to which she will not read three times a week for three months, and to compare its vocabulary with the group to which she is reading. Thus, she will see how much reading has influenced the vocabulary change when compared to the natural vocabulary change in the non-reading group. In other words, whether the change in the group to which she was reading is greater, does that group have a larger word pool in its vocabulary than the group to which she did not read.

glass wants to live in a world of super heroes and villains. he have lived all his life trying to be responsible for the creating the origin story of a super hero; he schemed and caused many incidents (many of them fatal) hoping that someday someone with superpowers would show up and save the day.

he knew himself very much. he saw himself as a villain of a real-life super hero story. he was aware of his strengths (more than smart enough for being manipulative and scheming) and weaknesses (having fragile bones and having to rely on his mind to succeed).