“一个”的“一”，实际口语里读什么调？
In 一个 (one + measure word), what tone does 一 actually take in speech?
全球翻车率（内测预估）
A一声 yī
yì shēng yī · 1st tone, yī
B三声 yǐ
sān shēng yǐ · 3rd tone, yǐ
✓二声 yí（四声前变调）
èr shēng yí（sì shēng qián biàn diào） · 2nd tone yí (tone sandhi before a 4th tone)
D四声 yì
sì shēng yì · 4th tone, yì
“一”字变调：四声前读 yí，一二三声前读 yì，单念才是 yī。没人告诉你？现在知道也不晚。
Tone sandhi: 一 becomes yí before 4th-tone syllables (yí gè), yì before others (yì tiān), and stays yī only in isolation or counting. Textbooks whisper this; speech shouts it.