Consider the following sentences:
- After his surgery, Raja hardly could walk.
- After his surgery, Raja could barely walk.
- After his surgery, Raja barely could walk.
- After his surgery, Raja could hardly walk.
Which of the above sentences are grammatically $\text{CORRECT}$?
- $\text{(i) and (ii)}$
- $\text{(i) and (iii)}$
- $\text{(iii) and (iv)}$
- $\text{(ii) and (iv)}$