(Due to ) presistent inbreeding, self-pollinating plants (have) genetically more uniform than cross-pollinated plants, which harbor more genetic (variability).

上广州XDF的时候听lili老师说这道题是“。。。。。无数个热血青年葬身的墓地”，但是在这之前对题目的讲解我正好走神了，现在再看回这道题，好郁闷，希望GGJJ能进来讨论一下，谢谢！~