尿液检测有哪些应用？
参考答案：
As a child, Johnson would sit on the steps alone, _______ the sun ______ down.
A．watching; go
B．watching; went
C．watched; going
D．watched; went
在煮饭时，锅盖被水蒸气顶起来，水蒸气对锅盖做了______，水蒸气内能______，从能量观点看是______能转化为______能．
