The correct answer is: A. He said that I can’t bathe in this sea because it’s very rough.
The speaker is saying that the sea is too rough to bathe in. The reason for this is that the sea is very rough. The speaker is using the word “because” to indicate the reason for the statement.
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 the sea as it was very rough. The speaker is saying that the listener cannot bathe in the sea because it is very rough.
Option D is incorrect because the speaker is not saying that the listener cannot bathe in the sea since it was very rough. The speaker is saying that the listener cannot bathe in the sea because it is very rough.