The Atlantic Ocean is only half as big as the Pacific, ______ it

The Atlantic Ocean is only half as big as the Pacific, ______ it is still very large.
A、but
B、and
C、so
D、therefore
【正确答案】：A
【题目解析】：本题考查句子的逻辑关系。前后并列句的意思有转折，所以用but。