Looking at my mother's ___________ face, I regretted not having told her my whereabouts on the phone.

According to the latest research, getting enough sleep is _____ to maintaining good health and reducing stress.

Between 4.5 and 3.8 billion years ago, the earth became so ______ that it was not clear whether the shape would last or not.

We must create a safe and ______ international environment of lasting peace.

As we all know, children are always ________ about everything fresh to them.