The New York Times reports that this years fire season hasnt been as bad as it has been for the previous two years, butthats little comfort to those witnessing the flames flare up.
上句flare up是否是witness的宾语补足语？即witness sb do sth这种结构呢？
He witnessed two masked men jumping into a car.jumping是现在分词还是动名词，为什么？
No one witnessed his(=him) leaving the house.leaving是现在分词还是动名词，为什么？
在V+sb/sth+doing+sb/sth这种类似的结构里，
1）如何准确判断doing是现在分词还是动名词，判断的依据或方法是什么呢？
2）判断是现在分词或动名词，对句意的理解究竟有何不同呢？这是我最疑惑的地方！