Here is kind of rule that I have based on my experience
Whenever Sine is there more chances of perfect tense
Whenever there is proper time mention like last 20 years--- less chances of perfect tense.--- However What will say abt following sentence
In last 20 years, california wines have/are gained respect
Whenever Sine is there more chances of perfect tense
Whenever there is proper time mention like last 20 years--- less chances of perfect tense.--- However What will say abt following sentence
In last 20 years, california wines have/are gained respect
