用双硫腙比色法测定铅时,为了消除其他金属离子的干扰,应采取的措施是()。
A、控制pH=8.5~9.0
B、加氰化钾
C、加柠檬酸铵
D、加盐酸羟胺
参考答案:A, B, C, D
To keep_____, we should do more exercise and eat _____junk food.
A.healthy; more
B.unhealthy; more
C.unhealthy; less
D.healthy; less
白求恩是何方人士?