A：We both like helping people.
B：We both like playing table tennis.
C：We often help old people cross the street.
“（鸦片战争后）时至今日，农村破产，日益剧烈，农民痛苦，日益深刻，各乡村普遍出现了一种杌齁不安的现象。农民莫不纷纷离村，徙居都市。”（董汝舟《中国农民离村问题之检讨》），农民“徙居都市”的主要原因是（ ）
