问题补充：
To walk from Tian anmen Square to the Summer Palace is too far.(改为同义句）
答案：
To walk from Tian anmen Square to the Summer Palace is too far.
= It is too far to walk from Tian anmen Square to the Summer Palace.
注：变化句型采用It做形式主语,而不定式短语to walk from Tian anmen Square to the Summer Palace放在句尾做真正的主语.
