In front of ______ remained of my old house,I took some pictures,which called up my childhood.
It is pretty well understood_______controls the flow of carbon dioxide in and out of the atmosphere today.
Mary got into acting purely _____________.
It is no use thinking about your ________ youth.
---Must he come to sign this paper himself? ---Yes.He______ .
I wonder how he could __________ not handing in his maths exercises yesterday, for his maths teacher is always strict with his students.