There are days in a week. The day is Saturday.
A:seven; seven
B:seven; sixth
C:seventh; seven
D:seven; seventh
计算.
207×3=____ 530×9=____
孝敬父母长辈是我们应尽的责任,这一责任主要来源于( )①法律 ②习俗 ③道德 ④承诺