Answer: The correct answer is 1) leaves.
Cactus is a desert plant that possesses thick, enlarged, and leafless stems that are covered with sharp spines or spikes. These sharp cactus spines are the modified leaves that provide them an extra advantage for surviving in desert.
Cactus spines provide protection against predator (as they are very sharp) and prevent the loss of water by reducing the flow of air near the cactus and giving them some shade.