هریک از اعداد را بررسی می‌کنیم: $x=1\Rightarrow \frac{1\times 4}{4}=1\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x=2\Rightarrow \frac{4\times 9}{4}=9$ $x=3\Rightarrow \frac{9\times 16}{4}=36\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x=4\Rightarrow \frac{16\times 25}{4}=100$ $x=5\Rightarrow \frac{25\times 36}{4}=225\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x=6\Rightarrow \frac{36\times 49}{4}=441$ پس به‌ازای $2$ عدد عبارت زوج است. بنابراین گزینۀ $2$ پاسخ است.