The nurse is instructing an unlicensed assistant on how to collect a urine specimen from an indwelling catheter. Which of the following statements indicates that the assistant understands the instructions

A．"I will empty the catheter drainage bag, have the client drink some water, and an hour later collect the urine that drains into the bag. "

B．"I will get a sterile syringe and remove urine from the catheter through the collection port to place in the specimen container. "

C．"I should collect urine from the catheter drainage bag at the end of the shift and place it in the specimen container. "

D．"I will disconnect the drainage tube from the catheter and let urine run from the catheter into the specimen container. "

引起转化炉温不稳定的原因是（）。

A.转化进料量波动

B.部分火嘴燃烧不良

C.排烟温度低

D.燃料气组分变化大