But their parents never explained why he'd been attacked or by whom, or mentioned that the stranger sitting in the living room from then on was a bodyguard - and the children knew better than to ask. 

老师好，请问句尾的than “to” ask怎样理解呢，than后面的动词形式通常不是应该前面的一致么。 

>>>>  know better than to do 是固定表达，一般词典上都会收录

我只能告诉你，后面用do/doing都错

（know better than to do XXX 意思是“还不至于(无知到)去做XXX”）

Three days later - her nose still in bandages, her eyes still black and swollen - 13-year-old Margo made her own way home to Scotland. 

这段话的结构我也不太懂。three days later 后面的 her nose 和her eyes 后面都没有加“is”，这是不是和句中“－” 这个符号有关呢？13－year －old 我倒是能明白在句中是作形容词用的。

>>>> 这是独立主格结构，如

The man came in, a book was in his hand. (X)

---> The man came in, a book being in his hand. (√)

---> The man came in, a book in his hand. (√√)

---> The man came in, with a book in his hand. (√√)