The air quality in the city，________ is shown in the report，has improved over the past two months.(2012·福建，23)
A．that B．it C．as D．what
(2013·北京，26)—What do you think of teaching，Bob?
—I find it fun and challenging.It is a job ________ you are doing something serious but interesting.
A．where B．which C．when D．that
(2013·福建，24)It's helpful to put children in a situation ________ they can see themselves differently.
A．that B．when C．which D．where
Whatever is left over may be put into the refrigerator，________ it will keep for two or three weeks.(2011·安徽)
A．when B．which C．where D．while
Sales director is a position ________ communication ability is just as important as sales skills.(2012·重庆)
A．which B．that C．when D．where
(2010·山东)That's the new machine ________ parts are too small to be seen.
A．that B．which C．whose D．what
