I would like practice English, too. My Skype : ricky_huye

一般情况下 其实可以混用 at college /in the university. 在大学期间。但是如果专门指具体的哪个大学 大多数用university . 比如北大 peking university ,不是Peking college.另外college 还指学院，university 没有这个含义。

Swear by sth means you trust it can be relied on to have some effect, such as She swears by the God

Excellent explanation !

And z is like z in the word zero, C is like zw in the word of Zweig or in the German number Zwei

When you pronunce Z, it's voiced consonant ,ur throat trembles, and when you pronounce C, it's non-voiced consonant, your throat doesn't tremble

For learning mandarin, Chinese folk songs or red songs are good choices!