在食物链A→B→C中，能量逐级递减。其原因不包括（ ） A． 总有一部分A和B会自然死亡而给分解者分解 B． B、C摄入的能量总有一部分未被利用 C． A
— It’s getting late. Mother must be waiting for us to have dinner. — In that case, we ______. A. had better leave B. must have left C. need have
无色的混合气体甲，可能含有 NO、CO2、NO2 、NH3 、N2中的某几种。将100 mL甲气体经过如图实验装置的处理，结果得到酸性溶液，而几乎无气体剩余。则甲
完形填空（共20小题，每小题1.5分， 满分30分） Last year, I was speaking at a gathering of wealthy male investors. The organizers posted the 36 of a survey showing that only
用均匀的电阻丝围成的正方形导线框ABCD，如图所示。若分别将A、B两端和A、C两端接在同一个电源两端，则两次通过BC的电流之比为_______________。A
设k>0，若关于x的不等式kx+≥5在(1，+∞)上恒成立，则k的最小值为 .
Jim likes ______ games with me. A．play B．playing C．plays D．playes
The car _______ in Germany in the 1960s looks old now. A. produced B. producing C. to produce D. which produced
的解是 
.
；