I am very ____________ about expressing my opinions in public in case I may make mistakes.

 Whenever a patient needs an injection of Penicillin, the doctor does need to make sure whether his patient is ___ to the medicine.

Both the summer and the winter Olympic Games are held every four years on a _______ basis.

—Our family will go to Australia for a holiday. —Oh, really? That sounds __________!

—I really hope we can see Zhou Xun in Hangzhou this time. —Maybe, if we are______.