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[化] 反馈作用
🧩 词语组成解析
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[bæk]
n. 背，背部;背面，反面;后面，后部;（椅子等的）靠背;
vt. 使后退;支持;加背书于;下赌注于;
vi. 后退;倒退;
adj. 背部的;后面的;以前的;拖欠的;
adv. 以前;向后地;
🗣️ 情景例句
She was still beautiful at the age of forty.
她活到四十岁仍然很美。
Nothing is more precious than time.
世上最宝贵的莫过于光阴。
Sparks were emitted from small black boxes and red lamps flashed on and off angrily.
小黑盒子里迸出火花，红色灯泡发怒似地忽明忽暗。