I would say b and c, since unfasten and clench are basically antonyms and those answers both have antonyms
Explanation:
An answer for this is:
"The world is very very big!
There are so much mysteries!
There is so much fun as dangerous things! More and more things you learn about world and its complexities, more and more things you understand that you don't know about them! But... You will never understand it completely!
Answer:
both dairy products and leafy green