—I think you can’t believe I had to pay $20   a haircut?—You should try the barber’s       I go. It’s only $5.

When you cross the street, you can never be _______ careful.

She devoted herself___to her research and it earned her a good reputation in her field.

--- Tomorrow we’ll go hiking in the mountain to experience nature.---- ___ it rains heavily when we are still halfway?

Make sure to turn off the gas after you take a bath, which would ___ cause danger.