If the question is about the individual habits of a student, then I believe that the sentence should read, "There are two defects in your studying." I believe this because the practice of studying, how a student prepares, is the subject of scrutiny in the sentence. The "defects" asserted would most likely be associated with how Ramesh prepares. In this case, the word "studying" would be of proper use. There could be another instance where the other term of "studies" or "study" could be used. If the timbre of question is directed about something that has been produced or a series of works constructed by Ramesh, then one could state that the manner in which the data has been collected or the arguments posed are insufficient. In this case, the topic of the statement is not about what Ramesh does, but rather at what Ramesh has created or produced. In this light, the preceding statement might be about what Ramesh argues and has written, in which case, one could say, "There are two defects in your study" or "studies." In one statement, the term "study" is used as a verb, or course of action, while in the other, it is used as a noun, or thing.