1. She was entering the subway. At that thie, the dog felt that his old master is near. "On the subway", he barked loudly. People sitting on their seats were surprised.

Question

(Is the expression in the quotation marks correct? Which expression do we have to use? Do we put 'train' at the back?)

2. On the subway
3. In the subway
4. On the subway train
5. In the subway train

Answer 1

She was entering the subway. At that time, the dog felt that his old master was near. "On the subway," he barked loudly. People sitting nearby were surprised.

If you say or write "on the subway," you don't need to add the word "train."