THE CHRISTMAS TREE --- A LOT OF THINGS SINCE YESTERDAY BY MY SISTER...

1/ The Christmas tree --- a lot of things since yesterday by my sisters.

everywhere for hundreds of purposes for ---(20)--- no one could have imagined

A. have been decorated

B. has decorated

they would be used. In fact, the computer which has gone out of control and

proves to be smarter –(21)--- the humans –(22)--- are its masters has become one

C. have decorated

D. has been decorated