In many laboratory experiments, participants generally seem to recall items that have pleasant associations items that have an unpleasant association.

More accurately

Explanation:

Pleasant associations are the links that imprinted a positive and good influence on mind of the person. Unpleasant links do not leave a pleasant impact on mind and thus, might fade away or become difficult to recall properly.

According to the question , pleasant happening and things cab be recalled more precisely as compared to unpleasant situations because of their positive and happy impact of those things that remains in mind .

productive most commonly means: achieving or producing a significant amount or result.

explanation:

productive can also mean:

these depend on how the word productive is used. most likely productive will mean   achieving or producing a significant amount or result.

i believe your answer is mountains.