Is confounding a major threat to internal validity

In 100,000 years, the rotation of earth will be slower by how many seconds?

When were the exodus of farm workers during the depression

Catherine sat down will all of her income details from the past year to calculate the total income she had in that period. after she created a consolidated income statement, she deducted some tax-exempt income details from the statement. what term would catherine use for this final income calculation?