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When an acidic pH less than 6 changes to base pH which is more than 7, if an indicator is present we can see the color change from acid to base or viceversa
it occurs
German
"Has/have occurred" is the present perfect tense. "Already" is an adverb.
Uniformitarian philosophy views the relationship between the present and past as consistent over time, suggesting that the same processes and natural laws that operate today have been constant throughout Earth's history. This perspective underpins the idea that the geologic features and processes we see today are the result of gradual, slow changes that have occurred over long periods of time.
It just change the tense
It's present perfect tense.
It is "changes".
The perfect tense of "already occur" is "has already occurred."
The past tense of "to occur" is occurred.
Both the simple present and present perfect tenses are used to talk about actions in the present. However, the simple present is used for general truths or habitual actions, while the present perfect is used to talk about actions that occurred at an unspecified time in the past with a connection to the present.
Yes of course, the sun has been present for about 6 billion years, the earth has been present for about 4.5 billion years, recorded ice ages occurred between about 300,000 years ago until about 10,000 years ago.