______的定义是指相邻生态系统之间的过渡带，其特征是由相邻生态系统之间相互作用的空间、时间及强度所决定的。
参考答案：群落交错区
He makes about $1000 every week，much ______ is spent on books.
A．of which
B．in that
C．among which
D．of it
下列哪项不是痢疾的必有症状
A．里急后重B．腹痛C．下痢赤白脓血D．痢下白冻E．肛门灼热
