Whom send Canadian woman at school?

[Duo from Bulgaria]

English Language Tests, Intermediate level

ESL/EFL Test #156 "Phrasal idioms with the verb 'drop'", question 5

A 27-year-old Canadian woman confused the weekend with a weekday and ......... her 6-year-old at school on a Saturday.

(a) dropped off
(b) dropped out
(c) dropped behind
(d) dropped in

English Language Tests, Intermediate level

ESL/EFL Test #156 "Phrasal idioms with the verb 'drop'", answer 5

A 27-year-old Canadian woman confused the weekend with a weekday and dropped off her 6-year-old at school on a Saturday.

Correct answer: (a) dropped off
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I really can not understand the sense of this sentence.Whom send CANADIEN woman at school.Something missing.Why YOU use phasal verbs here?They are so difficult.Sorry

Duo from Bulgaria

[Kitosdad]

Clarification.

A Canadian mother brought her child to school, and left him there,( Dropped him off ) because she had not realised that it was a Saturday, a day when children DO NOT go to school.

Is that more understandable ?.
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Englishman living in Germany.

[Koka]

I will reply instead of him YEs thnx Mr that was an awesome example !!! I got it !!!