Hot air balloons have burners to keep the air hot.动词不定式做定语还是做目的、结果状语?

问题描述:

Hot air balloons have burners to keep the air hot.动词不定式做定语还是做目的、结果状语?

Hot air balloons have burners to keep the air hot
to keep the air hot动词不定式做定语

其实to keep the air hot既是定语,也是目的状语,也是结果状语.
是burners的定语,也可作have burners的目的状语或结果状语.
这三种语态是有重叠区的,区分时首先从结构考虑,另外还要考虑上下文意思.
He bought a gun to kill the president.But he gave up later.这里不定式就是目的状语了,而其他两个语态都不适用.