第252句：

This law was declared unconstitutional by the Supreme Court on the grounds that general taxes were being collected to pay one special group of people.
最高法院宣布这项法律违反了宪法，因为普通税收都被收集起来，付给了某一特定的人群。

六级词汇讲解:

本句的主干是This law was declared unconstitutional...。on the grounds引导原因状语从句。
unconstitutional为constitutional的反义词，意为“违反宪法的；非立宪的”。the Supreme Court指“最高法院”。on the grounds that意为“因为；以……为理由”。

英语六级考点归纳
与ground相关的短语及用法如下：
from the ground up意为“从头开始”。如：
Don't give up. You can do it from the ground up.
别放弃，你可以从头开始做起。
break ground意为“开辟道路；改革”。如：
The new country will break ground on all aspects.
这个新国家将从各方面进行改革。
lose ground意为“撤退；被某人／某事物逐渐赶上”。如：
The leader was losing ground as other runners accelerated.
领先者在另lJ的赛跑者加速时，逐渐失去优势。