in OR on ??????

May be I really out dated from Education. This week my princess brenda having exam so as usual we will do revision base on the exercise given by teacher.

As usual I will correct her mistakes and remind her if do.

Me : Rou, Why you write SIT IN the chair, must be ON ya.

Brenda : No, is IN. Teacher say if somebody sit very comfortable like sofa ...must be IN but ON only for chair without armrest.

Me : ??????, are you sure ????

The next day, I go and double confirm with her ENGLISH teacher, she said is true, everything that with armrest must be IN the chair.

(like picture below....)


I really blur already now??????