I saw a spider on the wall 我看到牆上有一隻蜘蛛(on the wall介詞片語來修飾)。
I unexpectedly saw a spider on the wall .我意外(用副詞unexpectedly來修飾)看到牆上有一隻蜘蛛(用介詞短語on the wall來修飾)。
I unexpectedly saw a spider on the wall yesterday at around 8 a.m. 昨天早上 8 點左右(用介係詞片語at the 8 a.m來修飾),我意外地(用副詞unexpectedly來修飾)在牆上看到了蜘蛛(用介詞短語on the wall來修飾)。