单选题：Nancy enjoyed herself so much _____she visited her friends i..

— Will Johnson finish his homework today? — No, ____ we promised to give him some help.A. as though B. as ifC. even D. even if

— The problem is very difficult. I'm afraid you can't work it out.— _____ or not I can succeed, I'll have a try.A. If B. SinceC. Whether D. As

Simon thought his computer was broken _____ his little brother pointed out that he had forgotten to turn it on.A. until B. unless C. after D. because

Bob is determined to get a seat for the concert _____ it means standing in line all night for the ticket.A. so that B. as if C. even though D. however

Kids are not allowed to leave kindergartens _____ their parents come to pick them up.A. since B. unless C. althoughD. because