The boy’s bad behavior at school __________ his mother many sleepless nights.

 Though you've got a tight schedule these days, I should be ________ if you could spare time to attend our meeting today.

The on-line diary blog is a cultural _____, perhaps as essential as usual books we read.

The natural beauty of Jiuzhaigou ________ millions of tourists from all over the world every year.

I do ______ your timely help yesterday, without _______ I couldn’t have found the solution.