"become concerned" 是系表结构（系动词 "become" + 形容词 "concerned"），表示从原本不担忧/不关心的状态，转变为“开始感到担忧、关心或关注”（强调“变化的过程”）。
"become concerned" 后通常接介词短语或从句，核心是说明“担忧/关心的对象”，常见搭配如下：
about：后接“令人担忧的事物”（强调对某事的担心）；
for：后接“被关心的人/物”（强调对对象的关怀）。
示例：He became concerned about his daughter's safety after she didn't call home.（女儿没打电话回家后，他开始担心她的安全。）
Many people became concerned for the homeless during the severe winter storm.（暴风雪期间，很多人开始关心无家可归者。）
此处 "concerned" 侧重“与…相关、关注某事（而非单纯担忧）”，更正式。
示例：The school became concerned with students' mental health after several cases of anxiety.（几起焦虑案例后，学校开始关注学生的心理健康。）
As she grew older, she became more concerned with environmental protection.（随着年龄增长，她越来越关注环保。）
从句通常是“令主语担忧的情况”，从句谓语常用虚拟语气（should + 动词原形，should 可省略），或陈述语气。
示例：She became concerned that her son (should) fall behind in school.（她开始担心儿子会在学业上落后。）
The manager became concerned that the project might not meet the deadline.（经理开始担心项目可能赶不上截止日期。）
可在 "become" 后加副词（如 increasingly, deeply, growingly 等），突出“变化的程度”。
示例：The government has become increasingly concerned about rising inflation.（政府对不断上升的通胀越来越担忧。）
We became deeply concerned when we heard about the accident.（听到事故消息时，我们深感担忧。）
与 "be concerned" 的区别：
"be concerned" 表示“处于担忧/关心的状态”（静态）；
"become concerned" 强调“从无到有的变化过程”（动态）。
例如：
He is concerned about his job.（他担心工作。—— 状态描述）
He became concerned about his job after the company announced layoffs.（公司宣布裁员后，他开始担心工作。—— 变化过程）
"become concerned" 是表达“开始担忧/关注”的常用短语，核心是“变化”，需根据具体对象选择介词（about/for/with）或从句，结合修饰语可更精准传达情感强度。