Select the correct direct form of the given sentence.
He told her that he could not marry her then but he would surely do so the following year.

Correct option is B

The correct direct form is "He said to her, 'I cannot marry you now but I will surely do so next year.'"
The original indirect speech, "He told her that he could not marry her then but he would surely do so the following year," is converted back to direct speech.
The phrase "could not" becomes "cannot" and "would" becomes "will" to match the direct speech tense and perspective.