________ the difficult maths problem, I have consulted Professor Russell several times.
#88373
A
Working out
B
Worked out
C
To work out
D
Work out
推荐题目
When I handed the form to John, he said that Smith would be the best person ______. 
#97298
A
to send
B
for sending it
C
to send it to
D
for sending it to
 _______ of water makes Death Valley a desert, but it is by no means devoid.
#98028
A
Lacking
B
Being lack
C
Because of lack
D
Lack