1._______his return from Europe,he set to work on project.
A.As
B.At
C.Upon
D.For
2.Look out Don’t get too close to thehouse______roof is under repair.
A.whose
B.which
C.ofwhich
D.what
3.Don`t leave the water_______while you brushyour teeth.
A.run
B.running
C.beingrun
D.torun
4.Last month I came to Britain .MyEnglish has improved a lot______I use it all the time .
A.since
B.while
C.when
D.as