— What do you want to be in the future, Nick?
— I want to be _____ pilot(飞行员), it is _____ exciting(令人激动的，兴奋的) job.
A：a, a
B：a, an
C：the, an
D：a, the
与单细胞藻类相比，草履虫没有的结构是（ ） ①细胞质 ②液泡 ③细胞核 ④细胞壁 ⑤细胞膜 ⑥叶绿体
