They considered ______ a computer ,which was considered ______ a great help in their work.
A：to buy, to be
B：buying, being
C： to buy, being
D：buying, to be
下列有关人体血液和血液循环的叙述错误的是（ ）
日本的4个大岛中，面积最大的是北海道岛。
