Rabbit Borya likes cabbages and carrots very much. In a day he eats either 9 carrots, or 2 cabbages, or 1 cabbage and 4 carrots. During one week Borya has eaten 30 carrots. How mnay cabbages has he eaten during this week? 
选项为:A:$$6$$  B:$$7$$  C:$$8$$  D:$$9$$  E:$$10$$  请回答其中一个选项.