A:泪液中的溶菌酶可杀死沙眼衣原体
B:淋巴结内的吞噬细胞吞噬侵入人体的链球菌
C:胃液中的盐酸可杀死部分进入胃内的细菌
D:体内的天花抗体能防御天花病毒
-- English is widely used all over the country.
-- Yeah, it is such ______ useful language that my grandma decided to buy ______ English-Chinese dictionary to learn it.