When the author wants to introduce some relevant studies that others have done， he or she would usually use the following phrases except for：

When the author wants to introduce some relevant studies that others have done， he or she would usually use the following phrases except for：
A.considerable researches were conducted
B.the focus of this review paper is on…
C.some research works published in the last years on this subject indicate…
正确答案：the focus of this review paper is on…