1. Amy took a subway yesterday.
2. Amy took the subway yesterday.
3. Amy took two subways yesterday.
(Which expressions are grammatical?)
1 would not be usually used.
2. is fine.
3. should be -- Amy took two subway trains yesterday.
2. Amy took the subway yesterday.
3. Amy took two subways yesterday.
(Which expressions are grammatical?)
2. is fine.
3. should be -- Amy took two subway trains yesterday.