大剂量具有降低血胆固醇水平的是（）。
A.硫胺素
B.核黄素
C.吡哆醇
D.烟酸
E.叶酸
参考答案：D
121. The problem was that Einstein's family did not have enough money to pay for his further .
A．school
B．studying
C．education
D．Schooling
RNAV是（）缩写。
A.区域导航
B.精密导航
C.真实值导航
D.规则导航
