The more we prepare,______ difficulties we have.

. People have always been_______about exactly how life on earth began.

Her ________ look suggested that she was very _______ with the answer.

Please remember to remind them that the products inside are ________ and must be handled with great care.

As there is less and less coal and oil, scientists are exploring new ways of making use  of ______________   energy, such as sunlight, wind and water for power and fuel.