He kept yawning in class this morning. That is _____ he stayed up late doing his homework last night.
A. why B. how
C. because D. whether
I want to show you is my gratitude and respect for your continuous and selfless help.
A. That B. Which
C. Whether D. What
Everyone is different and that is ________ makes our world so much better.
A. that B. which
C. what D. who
We're considering students' request ______the school cafeteria should provide more kinds of food．
A． how B． what
C． that D． whether
It suddenly occurred to me I hadn’t locked my door．
A．which B．where
C．that D．whether
I still remember _______ the grand school used to be a abandoned airport two years ago.
A. how B. where
C. when D. why
