There is only one playground slide in this school，so the students have to take （）to use it.

单项选择题Which of the following is a back vowel in English？（）

A./ɜː/
B./ɔ：/
C./ʌ/
D./e/

单项选择题The similarity between the English consonants p ， b ，and m is that they are all（）.

A.fricative
B.plosive
C.labial-dental
D.bilabial