I just wonder _____ that makes him so excited.
What makes the space shuttle _____ is that it takes off like a rocket but lands like an airplane.
No one imagined that the apparently _____ businessman was really a criminal.
Mary had taken _____ to see that her guests had everything that they could possibly want.
Jack almost fell off the cliff, but managed to _____ until help came.
Don't _____ the news to the public until we give you the go-ahead (许可,准许).