This is the 5163rd most frequent Japanese word.
選べ
"選べ" means "Choose" or "Select."
Here, '選べ' is again in the imperative form for instructions or advice, emphasizing the cautious manner of choosing.
投票の際は慎重に選べ。
Be careful in choosing during the voting.
The word '選べ' here is used as an imperative form of the verb '選ぶ' (to choose), directed at the listener to make a choice.
好きな色を選べ。
Choose your favorite color.
In this sentence, '選べ' (can choose) is used in its potential form, indicating ability to select something.