对黏液毯的描述正确的是()
A.外层为水样层
B.内层为粘蛋白
C.其q-合有溶茵酶、干扰素、SIgA等生物活性物质
D.外层为粘蛋白
E.分泌腺
参考答案:C, D
人体缺乏某种维生素会引起坏血病,这种维生素是( )
A.维生素A
B.维生素B
C.维生素C
D.维生素D
Steve used to be quiet, but now he is . [ ]
A. outgoing
B. more quickly
C. noisy
D. quieter