问题
选择题
The scientists ________ on the new medicine for two years. They will succeed in no time.
A．work
B．are working
C．have worked
D．will work
答案
C
题目分析: 句意：科学家们已经研制这个新药两年了，他们马上就要成功了。 in no time马上；根据for
two years两年，可知时态为现在完成时，故选C.