As soon as he landed on the inflated landing mat, and with the crowd on its feet, Mike immediately began preparing for his next attempt at flight.

【答】As soon as he landed on the inflated landing mat 是时间从句；with the crowd on its feet 是“with 复合结构”。从作用上看，前者是“时间状语”，后者是“方式状语”， 它们都是修饰后面主句的谓语动词；是两个并列的成分，and 不可省略。

He sat leaning against the back of the seat with his legs stretched out straight in front of him.

【答】leaning against the back of the seat with his legs stretched out straight in front of him，是现在分词短语，作“伴随状语”，修饰谓语动词sat。其中，with his legs stretched out straight in front of him 是“with 复合结构”，作“方式状语”，修饰leaning。构成格式：with + 名词 + 过去分词短语。