A group of college students is participating in a memory study that involves performing the same task each day under different circumstances; however, as each day goes by, the students are obviously getting more comfortable with completing the task. Which threat to internal validity has confounded this study?

Idont know which one is right   but i know that c is wrong and a might be wrong

Early 18th century british industries were generally small scale and relatively unsophisticated. most textile production, for example, was centred on small workshops or in the homes of spinners, weavers and dyers: a literal ‘cottage industry’ that involved thousands of individual manufacturers. such small-scale production was also a feature of most other industries, with different regions specialising in different products: metal production in the midlands, for example, and coal mining in the north-east.two illustrations of 18t