Final answer:
Widespread unemployment is NOT a future challenge facing Europe because of low population growth, as this can lead to a reduced labor force, which may in fact reduce unemployment rates.
Step-by-step explanation:
The student asks which of the following is NOT a future challenge facing Europe because of low (or zero) population growth: a) widespread unemployment, b) a reduced labor force, c) smaller internal markets for local goods, or d) a reduced tax base. The correct answer is a) widespread unemployment. This is because low or zero population growth tends to lead to a reduced labor force, which can create a scarcity of workers and potentially increase demand for labor, reducing the likelihood of unemployment. Other challenges Europe may face due to low population growth include a reduced tax base, because there would be fewer people paying taxes, and smaller internal markets for local goods, due to the decreased number of consumers.