XY-4-18

In California today, Hispanics under the age of eighteen account for more than 43 percent, compared with a decade ago, when it was about 35 percent.

1. In California today, Hispanics under the age of eighteen account for more than 43 percent, compared with a decade ago, when it was about 35 percent.
2. Of the Californians under the age of eighteen, today more than 43 percent of them are Hispanic, compared with a decade ago, when it was about 35 percent.
3. Today, more than 43 percent of Californians under the age of eighteen are Hispanic, compared with about 35 percent a decade ago.
4. Today, compared to a decade ago, Californians who are Hispanics under the age of eighteen account for more than 43 percent, whereas it was about 35 percent.
5. Today, Hispanics under the age of eighteen in California account for more than 43 percent, unlike a decade ago, when it was about 35 percent.

这题为什么选C？ 我选了 B，考的是什么语法点？