问题
During China’s Golden Week, the first week of October, 650 million domestic tips were made in the country. The number of visitors to domestic travel destination was _____ of last year.
A:twice as big as;
B:twice as big as that
C:as big as twice;
D:twice the size;
B:twice as big as that
C:as big as twice;
D:twice the size;
正确答案是：
