This is a data sufficiency questions. What we have to remember before starting solving this question is that we do not need the exact answer. Rather we just need to understand if the given info. and statements are sufficient for us to get to a DEFINITE answer.
Now we are given in the stem that 17 students volunteering. These students belong to different school clubs. Each student belongs to exactly one club and there were representatives from atleast 3 clubs. Out of the 17 students, 5 belong to Drama club and 4 belong to the Chess club.
Thus, we have 5+4+other students from other clubs = 17
We have 8 students from other clubs. These students can all be from one club or can be from any number of upto 8 different clubs. What we need to find is the number of ways of choosing a 3 student team, such that none of them belong to the same club. For us to find this, we will need 2 pieces of information:
(a) The exact number of different clubs
(b) The exact number of students in each club
If our statements give us the above 2, we should be able to answer the question definitively. Let's check our statements:
Statement 1: Among the 17 students 3 represented the Robotics Club and 2 represented the Art Club
Thus, we are given 5 from Drama, 4 from Chess, 3 from Robotics and 2 from Art i.e. 14 out of 17 students we know about. For the remaining 3 students, they could be part of one single club or 3 different clubs. Thus there could be students from 5 to 7 different clubs with each club having some unknown number of students. This statement does not give us any information of either of the above two pointers. Hence, we can say it is not sufficient. (A) and (D) eliminated
Statement 2: Among the 17 students exactly one club was represented by fewer than 3 students.
From the stem, we need information about the remaining 8 students. This statement tells us that there is exactly one club with 1 or 2 students. We cannot know if this club has 1 or 2 students. Also, we do not know exactly how many other clubs we have represented and exactly how many students representing each such club. This statement also gives us no information about either of the above pointers. Hence, we can say this statement is not sufficient. We can eliminate (B).
Both Statements Together: From the stem and Statement 1 we know that we have the combination of students as below:
5 Drama, 4 Chess, 3 Robotics and 2 Art = 14 students
We need info. about the remaining 3 students. If you see our analysis of statement 1, we said that we could have 3 students from one club or 1 student each from 3 different clubs or 2 from one club and one from the other. There was no definite way of saying just using statement 1.
But now, when we take both statements together, Statement 2 tells us that exactly one club has fewer than 3 students who represent it. From the above info. we can see that Art is that club. Thus, the only way we can have the remaining 3 students is them being from the same club.
Thus the combination becomes,
5 drama, 4 chess, 3 robotics, 2 art and 3 from one other club.
This answers both the above pointers we needed information on. THus, we can say both statements together are sufficient. (C) is the answer