According to the given question, we have 40 students in class.

Statement 1: Priya's rank is 31st from the bottom means Priya is above 30 persons in a class of 40 and below the 9 persons in a class of 40. So, Priya's rank out of 40 from the top is 10th ($40-30$). Also given in this statement that Priya is 4 ranks below Seema.

So Seema's rank is 6th ($10 - 4$).

Therefore statement 1 alone is sufficient to answer the question.

Statement 2: Ena is 37th from the bottom means Ena is above 36 persons in a class of 40 and below the 3 persons in a class of 40, So Ena's rank out of 40 from the top is 4th ($40 - 36$). Also given in this statement that Ena is 2 ranks above Seema.

So Seema's rank is 6th ($4+2$).

Therefore statement 2 alone is sufficient to answer the question.

Hence, Either Statement-1 alone or Statement-2 alone is sufficient to answer the question.