亚硒酸钠（Na2SeO3）能消除加速人体衰老的活性氧，其中硒（Se）的化合价为 [ ]
A．+1
B．+2
C．+3
D．+4
答案：D
标有“6V 12W”的灯泡正常发光时，灯丝的电阻是______Ω．
If _____ without following the doctor’s instructions, the medicine may have serious side effects.
A．Taken
B．to be taken
C．Taking
D．being taken
