모든 콘텐�?기사)�?저작권법의 보호�?받는 �? 무단전재, 복사, 배포 등을 금합니다. If a grammatical principle that is certainly extra to 서툴�?is a vowel �?and there is no other selection aside from a vowel �?then that grammatical basic principle cannot be included to 서툴�? In exercise, the wo