Final answer:
The correct question tag for the sentence "And so is your teacher,_______?" is "isn't he" or "isn't she", depending on the teacher's gender. It's used to ask for agreement or confirmation in spoken English.
Step-by-step explanation:
The sentence "And so is your teacher,_______?" requires a question tag to be completed. To formulate the correct question tag, one must consider the main part of the sentence. Since 'is' is the auxiliary verb and 'your teacher' is the subject, the tag should be negative if the main sentence is affirmative. Hence, the correct question tag is "isn't he" or "isn't she" depending on the gender of the teacher. English question tags are designed to prompt confirmation and are used in spoken English to ask for agreement or to check something. The use of the correct question tag in this context is essential to maintain the grammatical integrity of the sentence.