“Where will you be tomorrow,” I said, “in case I have to ring you ?”

The correct answer is: B. I asked where he would be the next day in case I had to ring him.

The sentence “Where will you be tomorrow,” I said, “in case I have to ring you ?” is a question. The speaker is asking the listener where they will be the next day, in case the speaker needs to call them. The speaker is using the word “ring” to mean “call on the telephone.”

Option A is incorrect because the speaker is asking where the listener will be, not where the speaker will be.

Option C is incorrect because the speaker is asking a question, not making a statement.

Option D is incorrect because the speaker is using the word “ring” to mean “call on the telephone,” not “go around.”