While typing, Helen has a habit of stopping _____ to give her long and flowing hair a smooth.
The math’s problem remained confusing to the boy although ______ over and over.
As a rule, you can borrow only two books ______ in the library.
This kind of desk can be ______ to the height you need.
Mother was in the kitchen ______ lunch while I was ______ the coming exam.
—What do you admire the spaceman ______? —His bravery to travel around the earth ______ a spaceship all alone.