请英语高手帮忙看看有无语法错误,

俄...这要怎么说呢..
第一句可以改成 There are usually 2 - 4 XXX in a group.
如 xxx = 人 那就 There are usually 2-4 person in a group
如果 xxx 是东西的话 也可以是 There are usually 2-4 xxx per group.
因为要有一个名词才成立 除非前文已经提过了 那么可以 There are usually 2 to 4 in a group.
第二句 太对不住了 不符合逻辑.看不懂...