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