please my teacher tell me what sentence is righrt
1) Is this your key or is it mine ?
2) Is this your key or it is mine ?
The conjunction "or" joins identical structures. Notice in A. and B. below how the word "is" is distributed. In A. it's at the beginning, whereas in B. it's at beginning and the end:
A. is this or is it
B. is this or it is
The correct form is A. "Is this your key or is it mine?"