$1.$ My English is a bit rusty. I haven't used it for years. (RUST) (ta có 1 cụm "a bit rusty" : "bị hao mụt ")

$2.$ My brother trained to be a teacher but then became a tour guide. (GUIDANCE) ( a tour guide: người hướng dẫn viên du lịch )

$3.$ Due to the flexibility, an English word can operate as a noun, a verb, and an adjective. (FLEXIBLE) ( đứng sau "the" là 1 danh từ)