Answer: C. about 3%
Step-by-step explanation:
In 2006 , Number of dogs in U.S. dogs = 72 million
In 2010, Number of dogs in U.S. dogs = 70 million
The percent decrease in the number of dogs in U.S. Homes from 2006 to 2010 =
[tex]\dfrac{\text{Change in number of dogs}}{\text{Number of dogs in 2006}}\times100\%\\\\=\dfrac{(72-70)\text{ million}}{70\text{ million}}\times100\%\\\\=\dfrac{2}{7}\times10\%\approx3\%[/tex]
So, the percent decrease in the number of dogs in U.S. Homes from 2006 to 2010 was about 3%.
Hence, the correct option is C. about 3%