don't forget ______ to Aunt Mary(write)为什么填to write

don't forget ______ to Aunt Mary(write)为什么填to write
don't forget ______ to Aunt Mary(write)为什么填to write

don't forget ______ to Aunt Mary(write)为什么填to write
三个用法
第一,forget to do,忘记还没做的事情
第二,forget doing忘记已经做过的事情
第三,forget that-从句