我国的丘陵较多， 东部地区自北向南有______________、______________、______________等。
辽东丘陵 山东丘陵 东南丘陵
A student conducts an experiment in biology lab and discovers that the ratio of the number Of insects in a given population having characteristic X to the number of insects in the population not having characteristic X is 5:3, and that of the insects having characteristic X are male insects. What proportion of the total insect population are male insects having the characteristic X ？（）
A.A
B.B
C.C
D.D
E.E
霍乱毒素每个毒素分子含有1个A亚单位和几个B单位（）
A.1～3
B.2～4
C.3～5
D.5～7
E.4～6
of the insects having characteristic X are male insects. What proportion of the total insect population are male insects having the characteristic X ？（）