To retrieve the sample, the technician had to carefully untie the intricate knot securing the specimen bag.
为了取出样本，技术人员不得不小心解开固定标本袋的复杂绳结。
Which choice best defines “untie”?
B — Loosen, undo a knot. “untie” means loosen, undo a knot.
Which word means “loosen, undo a knot”?
D — untie. “untie” means loosen, undo a knot.
untie — loosen, undo a knot. In Chinese: 解开，松开.
untie is pronounced /ˌʌnˈtaɪ/.
To retrieve the sample, the technician had to carefully untie the intricate knot securing the specimen bag. (为了取出样本，技术人员不得不小心解开固定标本袋的复杂绳结。)
loosen, undo, unfasten — all close in meaning to untie (loosen, undo a knot).
tie, fasten — each the opposite of untie (loosen, undo a knot).
Yes. untie is on the SAT Prep Basic list — the everyday academic words the SAT assumes you already have. The Digital SAT does not test vocabulary in isolation; words like this one are tested through Words in Context questions, where you choose the word that completes a passage most logically and precisely.
un(open)+tie(tie).