密度制约因素
参考答案：
是指作用强度的变化与昆虫种群密度有关的因素。
The church, which ____ back to the 17th century, is undergoing a complete restoration.
A．dates
B．comes
C．leaves
D．appoints
山药的功效是
A．补中益气，生津养血B．补气健脾，止汗安胎C．补气升阳，益卫固表D．补气养阴，清火生津E．益气养阴，补肺脾肾
