The correct answer is A. He said that I can’t bathe in this sea because it’s very rough.
The speaker is telling the listener that they cannot bathe in the sea because it is very rough. The speaker is using the word “because” to indicate that the reason for the listener not being able to bathe in the sea is because it is very rough.
Option B is incorrect because the speaker is not saying that the listener could not bathe in the sea if it was very rough. The speaker is saying that the listener cannot bathe in the sea because it is very rough.
Option C is incorrect because the speaker is not saying that the listener could not bathe in that sea as it was very rough. The speaker is saying that the listener cannot bathe in this sea because it is very rough.
Option D is incorrect because the speaker is not saying that the listener cannot bathe in this sea since it was very rough. The speaker is saying that the listener cannot bathe in this sea because it is very rough.