Immigration to the United States by people with shorter average height is no reason for th

Immigration to the United States by people with shorter average height is no reason for the decline in the average height in America because______.

A．Asians came to the United States only in recent years

B．Asians are taller than immigrants from other areas

C．the immigration by people with shorter average height is not large enough

D．immigrants of other ethnicities usually have good access to medical care and nutrition