（1）They are the principles，many of them，which I learnt at my mother's knee.
这里的many of them是插入语吗？插入语不会造成语法错误？后面的那个which是修饰principle还是many？
对的，那是插入语，语法没有错，which是修饰many of them 的。
(2）As for which beverage do people drink the most?
as for后面可以接句子吗?
as for后面是可以接句子，例: As for me, I like coffee more.
(3)dicussion和 debate有什么区别？
dicussion和 debate的区别是: dicussion 友善的讨论，而 debate 则是有争持性辩论。
(4）which is not completely bad 是“完全无害”还是“不是全是坏处”？
是“不是全是坏处”
(5）Coffee is a brewed drink prepared from roasted seeds otherwise known as coffee beans.这里的otherwise是什么意思？如果去掉对句意有何影响？
otherwise known 是 : "也被认识为" 去掉otherwise便会失去了句子的意思了。
(6）grow up as happy and healthy as possible 是否存在语法错误？应改成happily and healthily吗？
是的，要改为happily and healthily，因为它们是grow up的副词。
(7）serious和severe有什么区别？
serious 是严重 severe 是 very serious 很严重。
(8)do the very best for sb是把the very best看成名词吗？
跟在介词the 的後面 very best 即成了名词。
(9）Which is better homemade or store bought food for your baby?是否存在语法错误？是否应改成Which is better for your baby，homemade food or store bought food?
语法有错误，应该是:Which is better for your baby，homemade food or store bought food?
(10)There simply may be times when making your own infant food is simply out of the question.这里的先行词times应该怎么解释？是“时候”的意思吗？不是不可数名词吗，为什么加s?
有详尽的解答必加分！！！
Time 若作时间，是不可数的如 : a lot of time. 但时候是可数的。如 : sometimes, many times, a lot of times.
a lot of time 和 a lot of times 是不同意思的，a lot of time 是 : 有很多时间。 a lot of times 则是 : 很多时 / 很多次 的意思。
