diff --git a/1000-hours/sounds-of-american-english/2.2.2-pb.md b/1000-hours/sounds-of-american-english/2.2.2-pb.md
index 6933f59f..b8ead74f 100644
--- a/1000-hours/sounds-of-american-english/2.2.2-pb.md
+++ b/1000-hours/sounds-of-american-english/2.2.2-pb.md
@@ -8,12 +8,14 @@ The pronunciation of p and b s
Both consonants naturally have a slight ʊ sound, which is a byproduct of the air bursting past lips.
-中国学生在起初的时候常常分不清 *please* 和 *police* —— 可事实上，这两个词的区别很明显：
+中国学生在起初的时候常常分不清 *please* 和 *police* —— 可事实上，这两个词的区别很明显，区别很多：
-Chinese students often struggle to distinguish between *please* and *police* at first when learning English. But they are distinctly different:
+Chinese students often struggle to distinguish between *please* and *police* at first when learning English. But they are distinctly different, and with many differences:
* *please* 只有一个音节：pliːz，而 *police* 有两个音节： pəˈliːs；
* *please* consists of a single syllable: pliːz, while *police* has two syllables: pəˈliːs.
+* *please* 之中 iː 是长元音，而 *police* 之中 `ɪ` 是短元音。
+* In the word *please*, the iː is a long vowel, while in the word *police*, the ɪ is a short one.
* 前者末尾的辅音是 z，后者末尾的辅音是 s；
* The final consonant in *please* is a z sound, whereas in *police*, it's an s sound.
* 最关键的，前者开头最多听起来是 pʊ，而后者不一样，是 p 和另外一个元音构成的音节： pə……