Hello, can you guys please help i need to asnwer this. Please help and answer the question below, best qnswer gets brainliest

Katie and her father are looking at the pipes around their house. they find that some of the pipes have rust on them, making them look and feel different than normal pipes. what kind of change have the rusted pipes gone through? a. a physical change b. a vibration change c. a chemical change d. a temperature change