passive voice

[ccdaphne]

Please change the following sentence in passive voice.
Thank you.

Girls tie ribbons on heads.

1) Ribbons are tied on heads by girls.
2) Girls' head are tied ribbon.
3) Ribbons are tied on girls' heads.

Which one is the best answer.

[Horsa]

The sentence itself is strange. However, since we are not told on whose heads the ribbons are tied it is reasonable to assume that they could also be tied on boys' heads. Hence the only acceptable answer is the first option.