Jimmy is always ______ for class. His teacher is not happy with him.
A：early
B：quickly
C：late
D：busy
双龙洞的外洞很____，像个____；从外洞到内洞的孔隙很____，只能容得下____；双龙洞的内洞很____，什么都看不见。
下列有关单倍体植株的叙述正确的是
