参考答案：D

解析：

Caregivers must use surgical asepsis when performing any procedure in which skin integrity is broken or a sterile body cavity is entered. Because it disrupts skin integrity and involves entry into a sterile cavity (a vein), inserting an IV catheter requires surgical asepsis. The other options require the use of clean technique to prevent the spread of infection. Hand washing cleans the hands; it doesn't sterilize them. The GI tract isn't sterile; therefore, irrigating an NG tube or a colostomy requires only clean technique.