A negative demand shock occurs when there is a sudden decrease in demand for goods and services in an economy. In the options provided:
A. Foreign consumers demand more US goods and services (exports) - This would increase demand, not cause a negative shock.
B. Foreign consumers demand less US goods and services (exports) - This would decrease demand for US goods and services, which constitutes a negative demand shock.
C. Increased domestic consumption spending - This would increase demand, not cause a negative shock.
D. Decreased income taxes - This typically increases disposable income and can lead to increased demand rather than a negative shock.
Therefore, the correct answer is B. Foreign consumers demand less US goods and services (exports).