Correct option is C
From the given statement following Venn diagram will be drawn-

Conclusions:
1. Some mobiles are watches. (True, implies that every mobile is a watch. Therefore, "some mobiles are watches" is a valid conclusion.)
2. All mobiles are books. (False, there is no information connecting mobiles and books in a way that would support this conclusion.)
Correct answer is (c) Only conclusion 1 follows.