Which of the following pairs constitutes a buffer?

Which of the following mixture constitute a buffer?

Which of the following constitutes a buffer ?

Which of the following pairs constitute isotones ?

Which of the following pairs constitute isotones ?

Which of the following pairs is wrong

Which of the following pairs do not constitute resonanting structures ?

Consider a block suspended from a light string as shown in the digure. Which of the following pairs of forces constitute Newton's third law pair ?

Which of the following pair is correct ?

Which of the following pair is correct ?

Which of the following constitute a food-chain?