A lot of language learning，________ has been discovered，is happening in the first year of life，so parents should talk much to their children during that period.(2012·安徽，29)
A．as B．it C．which D．this
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
