Pardon? I _____ quite catch you.I said I ______ the song before.
A：didn't, hadn't heard
B：don't, didn't hear
C：didn't, didn't hear
D：won't, hadn't heard
组词语。
宛____
怦____
婉____
砰____
堵____
虚____
赌____
虑____
（2015•威海）先化简，再求值：（1x+1-1x-1）÷4+2xx2-1，其中x=﹣2+3．
下列物质的用途与其物理性质有关的是（ ）
一只灯泡与变阻器串联后接在54伏的电源上，灯泡的额定电压是36伏，电阻是15欧，为使灯泡正常发光，此变阻器的规格应为（ ）
