Final answer:
The grievance that relates to the founding principle of 'unalienable rights' is option 2) The king refused to approve laws that supported natural rights. The king's denial of these laws undermined the colonists' unalienable rights.
Step-by-step explanation:
The grievance that relates to the founding principle of 'unalienable rights' is option 2) The king refused to approve laws that supported natural rights. The principle of 'unalienable rights' refers to the idea that certain rights, such as life, liberty, and the pursuit of happiness, are inherent and cannot be taken away by any authority. By refusing to approve laws that supported natural rights, the king was denying the colonists their unalienable rights.