______ was not until the early 20th century _____ the importance of his ideas was realized.

Of the two sisters, Lucy is ______ one, and she is also the one who loves to be quiet.

, I lost heart in English learning, but my teacher often said to me, “Keep on studying hard ,and you’ll succeed .”[ ]

Scientists ____ thousands of chemicalsbefore they decided on the right one in the end.

Having _____ no-meat day would be a goodway of encouraging _____ low carbon life-style.