The nurse is caring for a 10-year-old child with rheumatic fever. While obtaining the child's health history from the mother, the nurse should ask if the child recently had which illness ？（）

A．Strep throat.

B．Influenza.

C．Chickenpox.

D．Mononucleosis.

成段更换钢轨应事先将准备换入的钢轨按顺号运送到换轨地点。