---Mum, must I wash the dishes right now?
---No, you _________.
A:shouldn't
B:wouldn't
C:mustn't
D:needn't
下列电路图,开关S闭合后,两个电阻串联的是
在土地上连续耕种,使土地得不到____ ,土壤____ 逐渐下降。