During recessions, when some workers lose their jobs and have lower incomes, sales of durable goods (goods with a life expectancy of 3 years or more) decline. Apparently, durable goods are:

During recessions, when some workers lose their jobs and have lower incomes, sales of durable goods (goods with a life expectancy of 3 years or more) decline. Apparently, durable goods are:
A.complements.
B.inferior goods.
C.substitutes.
D.normal goods.
正确答案：normal goods.