In answering this question, you will need to examine the two documents and the ideas that emerged from both about natural rights.
A good answer would examine the phrases "life, liberty and property" (Locke) and "life, liberty and the pursuit of happiness" (Jefferson) as a foundation for a possible claim of plagiarism.
Jefferson's defense would not deny that Locke was a major influence on Jefferson but that Jefferson took it further than the idea that civil society is solely formed around the protection of property rights, which is why he included happiness instead of property.