Wagon trains -- groups of wagons -- rode in four lines across the land when they passed through dangerous country.

VOA: special.2009.03.30

And I've divided these into two groups, the big three and the more interesting four.

我将其分为两组，三大因素和四个有趣因素。

耶鲁公开课 - 心理学导论课程节选

The two groups were retested four years later, and the study compared the results with the first test.

VOA: special.2009.10.21

The competition is organized so the thirty-two teams play in eight groups,each with four teams.

VOA: special.2010.06.09

The students played in groups of four.

VOA: special.2009.10.21

After four months of begging her husband and petitioning human rights groups, Sally was finally getting her divorce.

VOA: standard.2010.03.27

"Mortality disparities were noted for all four major U.S.racial and ethnic minorities groups."

VOA: standard.2010.04.07