语法总结
How often...?
How often 询问频率，回答可用 once、twice、always、often 等。
例：How often do you visit them? Twice a year.
频率副词
always、usually、often、sometimes 放在实义动词前。
例：I often play chess.
How often 询问频率
How often do/does + 主语 + 动词原形？用来询问多久一次；回答可用 once、twice、every week 等。
例：How often do you visit them? I visit them once a week.
频率副词的位置
always、usually、often、sometimes 通常放在实义动词前，be 动词后。
例：I often write e-mails. She is always kind.
一般现在时第三人称
主语是 he、she 或单数名词时，行为动词通常加 -s/-es。
例：My grandpa lives in Beijing. He often plays chess.