Explanation:

• Under the WTO system, generally, countries are designated as developed, developing, and least developed countries (LDCs). Hence statement 1st is correct.
• There are no WTO definitions of “developed” and “developing” countries. Members announce for themselves whether they are “developed” or “developing” countries. Hence statement 2nd is incorrect.
• However, a country that announces itself as ‘developing’ does not automatically benefit from unilateral preference schemes and other members can challenge the decision of a member to make use of provisions available to developing countries. Hence statement 3rd is correct.