According to the professor, what are two factors that prevent the Nightcap Oak population

According to the professor, what are two factors that prevent the Nightcap Oak population from spreading？ Choose 2 answers.

A．The complex conditions required for the trees to produce fruit

B．The fact that the seed cannot germinate while locked inside the shell

C．The limited time the seed retains the ability to germinate

D．Competition with tree species that evolved more recently

此题为多项选择题。请帮忙给出正确答案和分析，谢谢！