To solve the given question, we need to determine for what cause CRY, an organization, works. The question provides us with four options:

• improvement of agriculture
• destitute women
• protection of child rights
• elimination of prostitution

Let's analyze each option to identify the correct one:

1. Improvement of agriculture: This option is related to initiatives or organizations that focus on agricultural development and support for farmers. CRY is not known to focus its efforts on agriculture.
2. Destitute women: Organizations working for destitute women focus on women's empowerment, protection, and welfare. CRY's primary mission does not revolve around this; it specifically targets child welfare.
3. Protection of child rights: CRY stands for "Child Rights and You" and indeed works primarily for the protection and promotion of child rights. This aligns with CRY's mission and activities, which include advocating for child education, health, and protection from exploitation and abuse.
4. Elimination of prostitution: While this is an important social issue, CRY does not primarily focus on this area. Its primary commitment is toward child welfare and rights.

Analyzing the options, it is clear that option 3, protection of child rights, is the correct answer. This matches the focus and activities of CRY, which is devoted to advancing the rights and welfare of children.