维生素B6在体内的活性形式是
A. 甲基钴胺素
B. 磷酸钴胺素
C. 吡哆醇
D. 磷酸吡哆胺
E. 氨基苯甲酸
位于上颌骨的是
A. 关节突
B. 关节窝
C. 翼腭窝
D. 翼肌窝
E. 尖牙窝
Without a passport, leaving the country is ().
A. in question
B. without question
C. out of the question
D. out of question
There is an abundant supply of cheap labor in this country.
A. a steady
B. a plentiful
C. an extra D. a stable