英语题选择题。请说明原因.选择题1.She will be a nurse _____ she graduates fo

英语题选择题。请说明原因.
选择题
1.She will be a nurse _____ she graduates form the school.
A.by the time B.at this time C.at that time D.at a time
2.Tom was disappointed that most of the guests ____ when he _____ at the party
A.left；had arrived B.left；arrived C.had left；had arrived D.had left arrived
3.—I wore sports shoes to the ball yesterday evening by mistake!
—Oh,my dear,you must be very ____ at the ball!
A.embarrassed B.satisfied C.tired D.surprised
请说明原因。