Economists have hypothesized that the widening gap between the wages of unskilled workers and skilled workers may be due to ?

A. decrease in the demand for unskilled workers because of increases in technology and increases in international trade
B. increase in the number of unskilled workers available due to immigration into the UK.
C. decrease in the demand for unskilled workers are more poorly educated
D. increase in the number of unskilled workers available because workers are more poorly educated