请帮我分析一下下面句子的意思或者用法：

1. Only the ruling Bharatiya Janata Party of India, an outfit with much less stringent entry criteria, can claim deeper ranks.（尤其是最后的claim deeper ranks 是什么用法？）

只有执政的印度国大党，一个入党标准不是很严格的政党，才会有更深层的等级。

2. Sheer numbers lend it a helpful lustre of legitimacy.(sheer应该如何理解？）

sheer为强调性形容词，用于强调程度之高或数量之多。光党员人数众多这一点就足以让该党带有合法的光环。

3. …perhaps because stricter enforcement of party regulations and renewed efforts to collect membership dues is making party life look less appealing.(is making 为什么用is？不应该用are吗？）

of party regulations and renewed efforts to collect membership dues作定语修饰enforcement（主语），因此谓语为单数is。

4. Some party cells have stopped allowing student applicants to retake party entrance exams, designed to test their knowledge of its history and constitution, and have begun requiring them to supplement their mandatory study sessions with character-building morning runs. (supplement…这半句是什么意思？）

and have begun requiring them to supplement their mandatory study sessions with character-building morning runs. 并且要求他们补充必修的学习课程以及培养性格的晨跑。to supplement...为不定式短语作requiring的宾语补足语。