I think this one is B - Statement (2) alone sufficient. Think of this as a venn diagram with two overlapping circles. There are students who study Japanese, students who study French and students who study both. We are told that the students who study both represent 4% of the overall French students and that at least 100 students study Japanese.

Statement(1) tells us that 16 students study both French and Japanese. We know that these 16 students represent 4% of the total French students, so there must be 400 students studying French. We also know that at least 100 study Japanese, but the exact number could be more or less than 400...Not Sufficient.

Statement(2) tells us that the number of students who study both represents 10% of the overall Japanese students. From the stem, we know that the same number of students makes up only 4% of the overall French students. From this we know that the number of French students must be larger than the number of Japanese students...Sufficient