glancing at the bits of wood and metal that lay around him1.lay around him 2.glancing at 是动名词做主语吗?it crashing into the courtyard below 为什么crashing加ing不加不可以吗？

glancing at the bits of wood and metal that lay around him
1.lay around him
2.glancing at 是动名词做主语吗?
it crashing into the courtyard below 为什么crashing加ing不加不可以吗？