Well, kindly hold on till like March 25th before accepting. If you didn't get a response frok Ottawa by March 25th then you can accept. But when you get a response from Ottawa and it is positive then you can decline Lakehead by emailing thth you have changed your mind.Now, as per lakehead email, If I want to accept the offer letter then I have to do before 27th March. But, I want to wait for ottawa response. If I accept lakehead offer then can I accept ottawa offer?
Let remain positive about your application to Ottawa.
All the best!