下列各句中，没有语病的一句是（ ）

Her parents’ quarrelling with each other _________ is the main cause of her family’s breaking up.

. However hard I tried to explain it to her, she just couldn’t understand. I found her impossible to .

Thanks for listening to my problem andgiving me your advice, Amy.—_________. That’s what friends arefor.

Just believe in yourself and continue working hard, and ______ your final goal will be achieved