"be serious about" 是一个表达态度的常用短语，核心意思是：
用来强调某人对某件事、某个人或某个目标持有严肃、专注、非随意的态度，不是“开玩笑”或“敷衍”。
短语中的 about 是介词，因此后面必须接名词、代词或动名词（动词-ing 形式），构成be serious about + 宾语 的结构。
根据宾语的不同（事、人、目标），短语的用法可分为以下几类：
He's serious about his work and never cuts corners.（他对工作很认真，从不应付了事。）
She's serious about her homework—she checks every answer twice.（她对作业很认真，每道题都检查两遍。）
I think he's serious about Lily—he invited her to meet his parents.（我觉得他对莉莉是认真的，他邀请她见父母了。）
Don't play with her feelings—she's serious about you.（别玩弄她的感情，她对你是认真的。）
They're serious about starting a business—they've already written a business plan.（他们创业是认真的，已经写好了商业计划书。）
Are you serious about learning the piano? You need to practice every day.（你学钢琴是认真的吗？得每天练习才行。）
否定：在 be 动词后加 not，表达“对……不认真”。
He's not serious about his studies—he skips class often.（他对学习不认真，经常逃课。）
疑问：将 be 动词提前，用于询问对方的态度。
Is she serious about quitting her job? That's a big decision!（她真的要辞职吗？这可是重大决定！）
"be serious about sth" 和 "take sth seriously" 意思相近，可互换使用，但结构不同：
He's serious about his work. = He takes his work seriously.（他认真对待工作。）
Do you take this exam seriously? = Are you serious about this exam?（你对这次考试认真吗？）
"be serious about" 是表达“认真态度”的高频短语，适用于口语和书面语，只要记住后面接名词/代词/动名词 ，就能准确使用啦！