Qui a mangé mon porridge ? Je ne le trouve nulle part.

1.   ?    Who has eaten my porridge? I can't find it anywhere.
2.   ?    Who ate my porridge ? I can't find it anywhere.
3.   ?    Who has been eating my porridge? I can't find it anywhere.

J'ai déjà vu cette fille, mais je ne sais pas si je l'ai rencontrée à l'université ou chez Jenny.

1.   ?    I met that girl somewhere, but I don't know if I met her at the university or at Jenny's.
2.   ?     I have seen that girl, but I can't tell whether it was at the university or at Jenny's
3.   ?    I have met that girl, but I don't know whether I met her at the university or at Jenny's.
4.   ?    I met that bird, but who knows where, the university or Jenny's?

Je cherche un cadeau d'anniversaire pour elle depuis trois semaines. J'y ai passé tout mon temps.

1.   ?    I am looking for a birthday present for her. I have spent all my time on that.
2.   ?    I was looking for a birthday present for her. I spent all my time on that.
3.   ?    I have been looking for a birthday present for her. I have spent all my time on that.
4.   ?    I have looked for a birthday present for her. I have been spending all my time on that.