why don't and couldn't i make a mistake in reference to your address,i wonder?
I don’t know why I made such awful blunder of his address; but as it was safely received,it is alright.I attributed my blunder to my non-infallibility and you are compelled to pardon me this time at least.Why don’t and couldn’t I make a mistake in reference to your address,I wonder?
这段是全段,怎么don't and couldn't?