— Where is your sister, Dick? I need her help.— Dad, she in her room. Let me help you instead.
A:sleeps
B:is sleeping
C:slept
D:was sleeping
有一种毛绒玩具的面料为羊毛(绒),内充物为无毒聚酯纤维。下列说法正确的是()
化学中有许多概念既是相对的,又是统一的,如图反映了饱和溶液、不饱和溶液、浓溶液以及稀溶液的关系.
设函数f(x)=x3+bx2+cx(x∈R),若g(x)=f(x)﹣f′(x)是奇函数,则b+c的值为____ .