1. He has been working hard on the farm for three hours.
2. He has worked hard on the farm for three hours.
(Which one is correct? Are both OK? Which one is commonly used?)
3. They have known each other since they were 13 years old.
4. They have been knowing each other since they were 13 years old.
(#3 is right, but #4 is not right. Right? Do you have rules for that? Would you let me know the website for the rule?)
#1 and #2 are both good. #3 is better than #4 which is awkward.
Sra
"They have known" means that they knew each other in the past and continue to know each other in the present.
"They have been knowing" is about the same, but just awkward phrasing, as Sra has said. It's not a common verb expression among native English speakers.
Both sentences in both sets can be grammatically correct, but the meaning they convey is slightly different.
1. "He has been working hard on the farm for three hours." - This sentence is in the present perfect continuous tense, indicating that the person started working on the farm sometime in the past, and they are still working on it at the time of speaking. It emphasizes the ongoing nature of the action.
2. "He has worked hard on the farm for three hours." - This sentence is in the present perfect tense, indicating that the person has completed working on the farm. It does not necessarily convey whether the person is still working or not.
For question 1, both sentences are grammatically correct, but the choice between them depends on the specific context and intended meaning. If you want to emphasize the ongoing nature of the action, you can use sentence 1. If you want to emphasize the completion and overall duration of the action, you can use sentence 2. Sentence 2 is more commonly used in general.
For question 2, only sentence 3 is correct:
3. "They have known each other since they were 13 years old." - This sentence is in the present perfect tense, indicating that the action of knowing each other started in the past and continues up to the present moment.
4. "They have been knowing each other since they were 13 years old." - This sentence is incorrect. In English, we do not use the continuous form of the verb "know" to describe ongoing states of knowledge or familiarity. Instead, we use the simple form "know" for such cases.
For further information on verb tenses and rules, you can refer to grammar resources such as:
1. "Grammarly" - an online grammar checker and writing assistant: https://www.grammarly.com/blog/
2. "English Grammar - Guide to English Grammar" - a comprehensive guide to English grammar: https://www.englishgrammar.org/