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-olds, read to them three times a week for three months, then measure their vocabulary size again. When she compares the average vocabulary at the two times, she finds that there was a significant increase in their vocabulary. Why can't she conclude that this is due to the reading?a. mortality/attrition effect. b. selection effect. c. history effect. d. maturation effect.

Maturation effect

Explanation:

Maturation is a factor that threatens the internal validity. The experiment does not happen overnight. The experiment can be happened in a couple of days, weeks, year and so on.

The dissertation experiment does not run for a long time. Many of the maturation effects occur within a very short period. It can occur within a few days. Many factors occur with subjects such as tiredness, boredom, and hunger inattention, etc.  

Thus Emma finds that there was a significant increase in their vocabulary. She does not conclude that it happened because of the maturation effect.

loess contribute to the flooding of rivers by providing the silt that is washed into rivers and constantly raises the bed of the rivers. this elevation above the surrounding flood plains and dams allow the river to overwhelm the dams and flood thousand of square miles of neighboring flood plains.

answer; i believe its called ; checks   and balances;