It is quite apparent that the aging population in China will cause _____ heavy pressure on ____ whole society in the future .

A．a, /

B．/ ;/

C．a ; the

D．/ ; the

红花的显微特征是（）

A.花粉粒3萌发孔

B.花冠、花丝、柱头碎片多见

C.花柱表皮细胞

D.草酸钙方晶

E.晶纤维