26. 下列何種是牙冠齲齒的主要致病菌?(A)轉糖鏈球菌 (Streptococcus mutans)(B)發酵乳桿菌 (Lactobacillus fermentum)(C)溶齒放線菌 (Actinomyces odontolyticus)(D)血鏈球菌 (Streptococcus sanguinis)