疱疹样皮炎有显著瘙痒症状。
参考答案:对
—What do you think we can do for our aged parents?
—You ____ do anything except to be with them and be yourself.
A.oughtn’t to
B.don’t have to
C.mustn’t
D.can’t
草原生态系统中,营养元素分级的依据是什么?