1. I have helped an old lady carry a big bag.
2. I have helped an elderly person cross a street.
3. I helped a foreigner find a subway station.
4. I have helped an Englishman go to a police station.
5. I have helped a stranger find a bookstore.
6. I have helped a Japanese find the way to Seoul Station.
(Are the expressions all grammatical? How about the use of articles?)
They are all correct -- including the articles. :-)
Yes, all the expressions are grammatical. However, there are some minor corrections you can make for clarity and accuracy. Let's go through each expression one by one:
1. I have helped an old lady carry a big bag.
- This sentence is grammatically correct. It describes an action where you assisted an old lady by carrying a large bag for her.
2. I have helped an elderly person cross a street.
- This sentence is grammatically correct. It describes an action where you assisted an elderly person in safely crossing a street.
3. I helped a foreigner find a subway station.
- This sentence is grammatically correct. It describes an action where you aided a foreigner in locating a subway station.
4. I have helped an Englishman go to a police station.
- This sentence is grammatically correct. It describes an action where you assisted an Englishman in getting to a police station.
5. I have helped a stranger find a bookstore.
- This sentence is grammatically correct. It describes an action where you aided a stranger in finding a bookstore.
6. I have helped a Japanese find the way to Seoul Station.
- This sentence is grammatically correct. It describes an action where you assisted a Japanese person in finding directions to Seoul Station.
Regarding the use of articles (a, an, the), they are used correctly in most cases. The only correction would be in sentence 4, where you can use "the" instead of "a" if there is a specific police station you are referring to. It would then be: "I have helped an Englishman go to the police station."