Option A - As 'Oh dear!' is an expression, we can't separate 'oh' and 'dear'. Also, a new sentence after the exclamation mark begins with a capital letter and an interrogative sentence should always end with a question mark. Hence, option A is incorrect.
Option C - As the given sentence is an interrogative sentence, we can't use an exclamation mark. 'Oh dear!' is an exclamatory sentence as it is used to declare. Hence, option C is incorrect.
Option D - 'Oh dear!' is an expression and the words 'oh' and 'dear' are not separated by a comma. 'Did I really hurt you!' is not an exclamatory sentence, it is an interrogative sentence. Hence, option D is incorrect.
Option B - The given sentence has an exclamatory sentence 'Oh dear!' which is punctuated properly with an exclamation mark. 'Did I really hurt you?' is a question and thus it ends with a question mark. Hence, option B is the correct answer.