Answer:
1. abandon and claim are antonyms
2. abundant and plentiful are synonyms
3. obstacle and barrier are synonyms
4. pursue and seek are synonyms
5. efficient and ineffective and antonyms
Step-by-step explanation:
Abandon means to leave behind, while claim means to state that something is yours. These are opposites, so they are antonyms.
Abundant and plentiful both mean you have plenty, so they are synonyms.
Obstacle and barrier mean something blocks you, so they are synonyms.
Pursue and seek mean to look for something, so they are synonyms.
Efficient means something works well, and ineffective means something does not work at all, so these are antonyms.