_________, some famous scientists have the questions of being both careful and careless.

A(n)____can use his drawings to tell about beautiful mountains, the blue sea and many other things.

18 The _____ I know him, the _____ I admire his abilities

She is said _____in the United States forfour years before she came back to work in our company.

My parents _______ have arrived at suppertime but their flight was held up due to the heavy fog.