单项选择题

Which of the following is  in the teaching video  of tongue twister?

A.I know. you know. i know that you know. i know that you know that i know。
B.The shells she sells on the seashore are all sea shells I am sure.
C.Betty beat a bit of butter to make a better butter.
D.Big black bug bit a big black bear, made the big black bear bleed blood.