正误判断如下：
I have read all the books, three of that were assigned by the professor last week. （误）
I have read all the books, three of which were assigned by the professor last week. （正）
I have read all the books, and three of them were assigned by the professor last week.（正。加连词and 成为并列句）
I have read all the books; three of them were assigned by the professor last week..（正。用分号表示并列，不加连词）
I have read all the books, three of them assigned by the professor last week..（正。独立主格结构）
Julie was good at German, French and Russian, all of that she spoke fluently. （误）
Julie was good at German, French and Russian, all of which she spoke fluently. （正）
We depend on the land from which we get our food.（正）