Final answer:
The possible length of the third side of a triangle with two given lengths of 7 feet and 12 feet is between 5 feet and 19 feet.
Step-by-step explanation:
The third side of a triangle must be shorter than the sum of the other two sides and longer than the difference between the other two sides. In this case, the two given sides have lengths of 7 feet and 12 feet. Therefore, the possible lengths for the third side are between 12 - 7 = 5 feet and 12 + 7 = 19 feet. Therefore, the answer is c. 19 feet.