句型转换
____ She often does her homework at night. (变为否定句)
She                              her homework at night.
____ We are cleaning our classroom now. (对划线部分提问)
                  you          now?
____ He likes pandas because they are very cute. (对划线部分提问)
                he        pandas?
____ I think he is in the classroom.（改为否定句）
I        think he        in the classroom.
____ Mr Black is a doctor.（对划线部分提问）
                Mr Black         ?

在显微镜下观察洋葱鳞片叶内表皮细胞和人的口腔上皮细胞时，都能看到的结构是（　　）

=____

白天教室内有不少同学出现打“呵欠”的现象，这是因为（　　）

核孔是具有选择性的核质交换通道，亲核蛋白需通过核孔进入细胞核发挥功能。下图为非洲爪蟾卵母细胞亲核蛋白注射实验，下列相关叙述正确的是(　　)