________________ in the United States declined from nine million in the 1970s to under five million in 1981. A. For a number of horses B. When the number of horses C. The number of horses
________________ in the United States declined from nine million in the 1970s to under five million in 1981.
A. For a number of horses
B. When the number of horses
C. The number of horses
D. That the number of horses