①洋葱根尖分生区细胞 ②变形虫细胞 ③大肠杆菌细胞
④蛙的红细胞 ⑤蛙的囊胚期细胞 ⑥人的造血干细胞
A:③⑥
B:③④
C:①⑤
D:②④
一 I have made great progress in spoken English since last year.
一 Well done! I am sure you'll be good at it soon.
当新的实验提供了新的视角,或有了新的观测发现时,原有的理论就会被修改,下列关于各个理论的修正中正确的是( )
——Excuse me, could you tell me ?——Go along this street until you see some buildings with golden roofs.